Mean Elasticities Research Articles

Correlation of shear-wave elastography stiffness and apparent diffusion coefficient values with tumor characteristics in breast cancer

We aimed to investigate the correlation between shear-wave elastography (SWE) and apparent diffusion coefficient (ADC) values in breast cancer and to identify the associated characteristics. We included 91 breast cancer patients who underwent SWE and breast MRI prior to surgery between January 2016 and November 2017. We measured the lesion’s mean (Emean) and maximum (Emax) elasticities of SWE and ADC values. We evaluated the correlation between SWE, ADC values and tumor size. The mean SWE and ADC values were compared for categorical variable of the pathological/imaging characteristics. ADC values showed negative correlation with Emean (r = − 0.315, p = 0.002) and Emax (r = − 0.326, p = 0.002). SWE was positively correlated with tumor size (r = 0.343–0.366, p < 0.001). A higher SWE value indicated a tendency towards a higher T stage (p < 0.001). Triple-negative breast cancer showed the highest SWE values (p = 0.02). SWE were significantly higher in breast cancers with posterior enhancement, vascularity, and washout kinetics (p < 0.02). SWE stiffness and ADC values were negatively correlated in breast cancer. SWE values correlated significantly with tumor size, and were higher in triple-negative subtype and aggressive imaging characteristics.

Assessing the Link between Vessel Size and Maritime Supply Chain Sustainable Performance

This study determines the relationship between the increase in size of dry bulk carriers and container ships and the changes in sustainable shipping performance. It measures the elasticities of shipping costs for bulk carriers and container ships. Using regression, it derives the functions of the daily and unit costs of shipping with respect to the size of dry bulk carriers and container ships. The estimated daily and unit cost elasticities and cost models reveal significant but diversified impacts of vessel size on dry bulk and container shipping cost and its components, other operating capital, and fuel costs. Findings: Dry bulk carriers and containership size mean elasticities of daily operating costs estimates respectively: total operating costs 0.291 and 0.552, other operating cost (labor cost included) 0.238 and 0.328, capital costs 0.329 and 0.765, fuel costs 0.289 and 0.462; dry bulker and container ship unit shipping mean elasticity respectively: full operating costs (−0.751) and (−0.553), other operating cost (−0.804) and (−0.782), capital costs (−0.713) and (−0.399), fuel costs (–0.757) and (−0.702). This research provides an insight into the impact of technology and the way the services are provided (irregular versus regular) on shipping cost and energy savings. The cost models can be used for estimating the savings in shipping costs resulting from handling larger vessels in seaports.

Toward a Difference Approach: A Discrete Meat Demand System

While the differential approach to economic analysis is useful, the difference approach is indispensable as almost all economic data are discrete, rather than continuous. Thus, we must to investigate the integration of the differential with difference approaches. We show a difference quotient corresponding to a differential quotient, which is generally called a derivative, and a partial difference quotient corresponding to a partial differential quotient, which is generally called a partial derivative. From these, the difference approach produces a discrete demand system with logarithmic mean elasticities as parameters that corresponds to a continuous demand system with point elasticities as parameters produced by the differential approach. These systems should satisfy each budget constraint: the former for finite-change variables and the latter for infinitesimal-change variables. Based on these, we consider a discrete meat demand system, apply it to monthly demand for fresh meat in Japan, and estimate it using a weighted RAS method. The estimated demand system has two desirable properties: each estimated demand (theoretical value) of the conditional demand function coincides with each observed demand, and this system satisfies the difference budget constraint.

Comparison of 2‐Dimensional Shear Wave Elastographic Measurements Using ElastQ Imaging and SuperSonic Shear Imaging: Phantom Study and Clinical Pilot Study

To compare the feasibility and clinical applicability of ElastQ imaging (Philips Healthcare, Best, the Netherlands) with that of SuperSonic shear imaging (SSI; SuperSonic Imagine, Aix-en-Provence, France) using an elastographic phantom and a pilot study of patients. Two-dimensional shear wave elastography measurement was performed by ElastQ imaging and SSI by 2 radiologists. An elastographic phantom with 5 target elasticities at 2 acquisition depths was used. The coefficients of variation and intraclass correlation coefficients (ICCs) were evaluated for repeatability and interobserver agreement, respectively. The mean elasticities of the systems at each target were compared. The proportions of measurements that were out of the range of expected values and measurement errors were calculated to determine accuracy. Liver stiffness (LS) was measured by both systems in 27 children and young adult patients with various liver diseases. Both systems provided high repeatability in elasticity measurements of phantom targets (coefficients of variation, 0.69%-15.82%), and there was excellent interobserver agreement (ICC, 0.992). Most (90%) mean elasticities of targets were significantly different between the techniques (P ≤ .002) and acquisition depths (P ≤ .004). ElastQ imaging had significantly lower proportions of out-of-range measurements and measurement errors (P ≤ .003) than SSI. In patients with liver disease, LS measurements of the systems were strongly correlated (ρ = 0.955; P < .001) and had excellent agreement (ICC, 0.951; P < .001). ElastQ imaging had comparably good results in terms of repeatability, interobserver agreement, and accuracy in the phantom model compared with SSI. The pilot patient study showed strong correlations in LS values between the systems.

Can Ultrasonographic Vascular and Elastographic Features of Invasive Ductal Breast Carcinoma Predict Histologic Aggressiveness?

To investigate if preoperative ultrasonographic vascular and shear-wave elastographic examinations can predict histologic aggressiveness. Preoperative ultrasonographic vascular features and shear-wave elasticities were retrospectively evaluated for 147 invasive ductal carcinomas. Vascular feature was assessed using four-tier vascularity score. Mean and maximum elasticities (Emean and Emax), and the lesion-to-fat ratio (Eratio) were documented. Histologic parameters were reviewed for tumor size, multiplicity, axillary lymph node status, lymphovascular invasion, histologic grade, estrogen receptor, progesterone receptor, human epidermal growth factor receptor2 (HER2), Ki-67, p53, and histologic subtype. Vascularity score and elasticities were correlated with histologic parameters and histologic parameters were compared between the group with low vascularity score and elasticities and the group with high vascularity score and elasticities using ANOVA, chi-squared test, and regression analysis. Vascularity score was independently associated with tumor size (p = 0.010) and HER2 (p = 0.007). Emean and Emax were associated with tumor size, histologic grade, and lymphovascular invasion, and Eratio was associated with tumor size, histologic grade, estrogen receptor, progesterone receptor, Ki-67, and histologic subtype (p < 0.05). Emean and Emax were independently associated with tumor size (p < 0.001). The group with high vascularity score and Eratio showed large tumor size (p < 0.001) and HER2 positivity (p = 0.039) in comparison to the group with low vascularity score and Eratio. Ultrasonographic vascular features were associated with tumor size and HER2. SWE elasticities were associated with tumor size, histologic grade, hormonal receptor, and histologic subtype. Therefore, preoperative vascular and elastographic examinations could predict histologic aggressiveness of invasive ductal breast carcinoma.

Does Shear Wave Elastography (SWE) parameters improve the differentiation the character of the thyroid lesions

The aims of study were to determine whether shear wave elastography (SWE) can improve the B-mode differentiation of thyroid lesions, determine the most accurate SWE parameter for differentiation, and assess the influence of microcalcifications (MCs) and chronic autoimmune thyroiditis (CAT) on SWE values. We examined 119 patients with 169 thyroid nodules who prospectively underwent B-mode US and SWE using the same US machine. The following parameters were assessed using SWE: mean elasticity within the entire lesion (SWE-whole) and the mean (SWE-mean) and maximum elasticities (SWE-max) for a 2-mm region of interest (ROI) in the stiffest portion of the lesion, excluding MCs. The discriminant powers of a GEE model including B-mode only and both B-mode and SWE parameters were assessed and compared using the area under the ROC curve (AUC), in association with pathological verifications. In total, 50 and 119 malignant and benign lesions were detected. Multivariate logistic regression analysis for B-mode parameters revealed that MCs [odds ratio (OR), 4.3, hypoechogenicity (OR, 3.13, and irregular margins (OR, 10.82) were associated with a higher OR for malignancy, while that for SWE parameters revealed that SWE-max was an independent parameter for the same (OR, 2.95). The AUC for the B-mode model was 0.85, while that for the model combining B-mode and SWE parameters was 0.87. There was no significant difference in the mean SWE values between patients with and without CAT.

Determining the hydrological responses to climate variability and land use/cover change in the Loess Plateau with the Budyko framework

Understanding and quantifying the impacts of land use/cover change and climate variability on hydrological responses are important to the design of water resources and land use management strategies for adaptation to climate change, especially in water-limited areas. The elasticity method was used to detect the responses of streamflow and runoff coefficient to various driving factors in 15 main catchments of the Loess Plateau, China between 1961 and 2009. The elasticity of streamflow (Q) and runoff coefficient (Rc) to precipitation (P), potential evapotranspiration (E0), and catchment characteristics (represented by the parameter m in Fu's equation) were derived based on the Budyko hypothesis. There were two critical values of m=2 and E0/P=1 for the elasticity of Q and Rc. The hydrological responses were mainly affected by catchment characteristics in water-limited regions (E0/P>1), and in humid areas (E0/P<1), climate conditions played a more important role for cases of m>2 whereas catchment characteristics had a greater impact for cases of m<2. The annual Q and Rc in 14 of the 15 catchments significantly decreased with average reduction of 0.87mmyr−1 and 0.18%yr−1, respectively. The mean elasticities of Q to P, E0 and m were 2.66, −1.66 and −3.17, respectively. The contributions of land use/cover change and P reduction to decreased Q were 64.75% and 41.55%, respectively, while those to decreased Rc were 75.68% and 32.06%, respectively. In contrast, the decreased E0 resulted in 6.30% and 7.73% increase of Q and Rc, respectively. The contribution of land use/cover changes was significantly and positively correlated with the increase in the percentage of the soil and water conservation measures area (p<0.05). The Rc significantly and linearly decreased with the vegetation coverage (p<0.01). Moreover, the Rc linearly decreased with the percentage of measures area in all catchments (eight of them were statistically significant with p<0.05).

Can continuous scans in orthogonal planes improve diagnostic performance of shear wave elastography for breast lesions?

Static shear wave elastography (SWE) is used to detect breast lesions, but slice and plane selections result in discrepancies. To evaluate the intraobserver reproducibility of continuous SWE, and whether quantitative elasticities in orthogonal planes perform better in the differential diagnosis of breast lesions. One hundred and twenty-two breast lesions scheduled for ultrasound-guided biopsy were recruited. Continuous SWE scans were conducted in orthogonal planes separately. Quantitative elasticities and histopathology results were collected. Reproducibility in the same plane and diagnostic performance in different planes were evaluated. The maximum and mean elasticities of the hardest portion, and standard deviation of whole lesion, had high inter-class correlation coefficients (0.87 to 0.95) and large areas under receiver operation characteristic curve (0.887 to 0.899). Without loss of accuracy, sensitivities had increased in orthogonal planes compared with single plane (from 73.17% up to 82.93% at most). Mean elasticity of whole lesion and lesion-to-parenchyma ratio were significantly less reproducible and less accurate. Continuous SWE is highly reproducible for the same observer. The maximum and mean elasticities of the hardest portion and standard deviation of whole lesion are most reliable. Furthermore, the sensitivities of the three parameters are improved in orthogonal planes without loss of accuracies.

Buy now, saved later? The critical impact of time-to-pandemic uncertainty on pandemic cost-effectiveness analyses

Background Investment in pandemic preparedness is a long-term gamble, with the return on investment coming at an unknown point in the future. Many countries have chosen to stockpile key resources, and the number of pandemic economic evaluations has risen sharply since 2009. We assess the importance of uncertainty in time-to-pandemic (and associated discounting) in pandemic economic evaluation, a factor frequently neglected in the literature to-date. Methods We use a probability tree model and Monte Carlo parameter sampling to consider the cost effectiveness of antiviral stockpiling in Cambodia under parameter uncertainty. Mean elasticity and mutual information (MI) are used to assess the importance of time-to-pandemic compared with other parameters. We also consider the sensitivity to choice of sampling distribution used to model time-to-pandemic uncertainty. Results Time-to-pandemic and discount rate are the primary drivers of sensitivity and uncertainty in pandemic cost effectiveness models. Base case cost effectiveness of antiviral stockpiling ranged between is US$112 and US$3599 per DALY averted using historical pandemic intervals for time-to-pandemic. The mean elasticities for time-to-pandemic and discount rate were greater than all other parameters. Similarly, the MI scores for time to pandemic and discount rate were greater than other parameters. Time-to-pandemic and discount rate were key drivers of uncertainty in cost-effectiveness results regardless of time-to-pandemic sampling distribution choice. Conclusions Time-to-pandemic assumptions can “substantially” affect cost-effectiveness results and, in our model, is a greater contributor to uncertainty in cost-effectiveness results than any other parameter. We strongly recommend that cost-effectiveness models include probabilistic analysis of time-to-pandemic uncertainty.

The impact of food prices on consumption: a systematic review of research on the price elasticity of demand for food.

In light of proposals to improve diets by shifting food prices, it is important to understand how price changes affect demand for various foods. We reviewed 160 studies on the price elasticity of demand for major food categories to assess mean elasticities by food category and variations in estimates by study design. Price elasticities for foods and nonalcoholic beverages ranged from 0.27 to 0.81 (absolute values), with food away from home, soft drinks, juice, and meats being most responsive to price changes (0.7-0.8). As an example, a 10% increase in soft drink prices should reduce consumption by 8% to 10%. Studies estimating price effects on substitutions from unhealthy to healthy food and price responsiveness among at-risk populations are particularly needed.

Environmental variance, population growth and evolution

Environmental fluctuations on time scales of one to tens of generations are increasingly recognized as important determinants of population dynamics and microevolution. Jonzén et al. in this issue analyse how the vital rates of red kangaroos depend on annual rainfall, and estimate the elasticities of stochastic growth rate to the means and variances of the vital rates, as well as to the mean and variance of rainfall. Their results demonstrate how ecological and evolutionary studies can benefit from including explicit environmental drivers when modelling populations, and from the use of mean and variance elasticities.

Stochastic demography and population dynamics in the red kangaroo Macropus rufus

1. Many organisms inhabit strongly fluctuating environments but their demography and population dynamics are often analysed using deterministic models and elasticity analysis, where elasticity is defined as the proportional change in population growth rate caused by a proportional change in a vital rate. Deterministic analyses may not necessarily be informative because large variation in a vital rate with a small deterministic elasticity may affect the population growth rate more than a small change in a less variable vital rate having high deterministic elasticity. 2. We analyse a stochastic environment model of the red kangaroo (Macropus rufus), a species inhabiting an environment characterized by unpredictable and highly variable rainfall, and calculate the elasticity of the stochastic growth rate with respect to the mean and variability in vital rates. 3. Juvenile survival is the most variable vital rate but a proportional change in the mean adult survival rate has a much stronger effect on the stochastic growth rate. 4. Even if changes in average rainfall have a larger impact on population growth rate, increased variability in rainfall may still be important also in long-lived species. The elasticity with respect to the standard deviation of rainfall is comparable to the mean elasticities of all vital rates but the survival in age class 3 because increased variation in rainfall affects both the mean and variability of vital rates. 5. Red kangaroos are harvested and, under the current rainfall pattern, an annual harvest fraction of c. 20% would yield a stochastic growth rate about unity. However, if average rainfall drops by more than c. 10%, any level of harvesting may be unsustainable, emphasizing the need for integrating climate change predictions in population management and increase our understanding of how environmental stochasticity translates into population growth rate.

Using a heterogeneous multinomial probit model with a neural net extension to model brand choice

AbstractThe multinomial probit model introduced here combines heterogeneity across households with flexibility of the (deterministic) utility function. To achieve flexibility deterministic utility is approximated by a neural net of the multilayer perceptron type. A Markov Chain Monte Carlo method serves to estimate heterogeneous multinomial probit models which fulfill economic restrictions on signs of (marginal) effects of predictors (e.g., negative for price). For empirical choice data the heterogeneous multinomial probit model extended by a multilayer perceptron clearly outperforms all the other models studied. Moreover, replacing homogeneous by heterogeneous reference price mechanisms and thus allowing price expectations to be formed differently across households also leads to better model performance. Mean utility differences and mean elasticities w.r.t. price and price deviation from reference price demonstrate that models with linear utility and nonlinear utility approximated by a multilayer perceptron lead to very different implications for managerial decision making. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Simultaneous Adoption of Herbicide-Resistant and Conservation-Tillage Cotton Technologies

If adoption of herbicide-resistant seed and adoption of conservation-tillage practices are determined simultaneously, adoption of herbicide-resistant seed could indirectly reduce soil erosion and adoption of conservation-tillage practices could indirectly reduce residual herbicide use and increase farm profits. Our objective was to evaluate the relationship between these two technologies for Tennessee cotton production. Evidence from Bayes' theorem and a two-equation logit model suggested a simultaneous relationship. Mean elasticities for acres in herbicide-resistant seed with respect to the probability of adopting conservation-tillage practices and acres in conservation-tillage practices with respect to the probability of adopting herbicide-resistant seed were 1.74 and 0.24, respectively.

Theoretical Derivation of Value of Travel Time and Demand Elasticity

Users’ value of travel time (VOTT) and their responsiveness to toll changes (elasticity) for different trip purposes in the presence of time-of-day pricing is explored for drivers on the New Jersey Turnpike (NJTPK). An analytical model is developed by extending DeSerpa's classical time allocation model and relaxing the constant marginal utility assumption. This model joins users’ time-of-day choices in the presence of time-of-day pricing and departure- or arrival-time restrictions. With traveler survey data collected to evaluate the NJTPK time-of-day pricing program, VOTT and elasticity functions for different departure-time choices and trip purposes are estimated. The main contribution of the empirical results is the finding that in the presence of time-of-day pricing applications, when the main choice of commuters is departure time rather than alternative routes or modes, VOTT and elasticity of a user are influenced by trip purpose, desired arrival time, and early or late arrival amount in addition to travel time, toll amount, and income parameters. Mean VOTT values range between $15/h and $20/h, and mean elasticities range between —0.06 and —0.18 depending on the departure-time choice and trip purpose. Elasticities calculated from traffic and travel time data reveal estimates that are in the range of —0.15 and —0.31. These relatively high VOTTs and low elasticities from the low traveler response to the minor toll differentials introduced by the New Jersey Turnpike Authority's time-of-day pricing program can have major implications in determining effective toll differentials for future time-of-day pricing implementations in highly urbanized areas, where income levels are relatively high, user flexibility is low, and possibilities to shift to other modes or routes are limited.

Using nonprofit organization-level financial data to infer managers' fund-raising strategies

Using IRS data from 1982 to 1994, this study finds the typical fund-raising elasticities in seven categories of nonprofit organizations to be between zero and one. These results are consistent with most nonprofit managers following intermediate strategies between pure program service maximization and pure organization size maximization. However, the distribution of fund-raising elasticities contains extreme observations that can disproportionately affect mean elasticities and standard deviations. As a result, prior researchers' tests of the difference of mean elasticities from zero may not properly characterize the behavior of typical nonprofit organizations.

Using nonprofit organization-level financial data to infer managers' fund-raising strategies

Using IRS data from 1982 to 1994, this study finds the typical fund-raising elasticities in seven categories of nonprofit organizations to be between zero and one. These results are consistent with most nonprofit managers following intermediate strategies between pure program service maximization and pure organization size maximization. However, the distribution of fund-raising elasticities contains extreme observations that can disproportionately affect mean elasticities and standard deviations. As a result, prior researchers' tests of the difference of mean elasticities from zero may not properly characterize the behavior of typical nonprofit organizations.

The demand for straw and feathers as litter substrates by laying hens

Consumer demand theory has been applied to investigate behavioural demands and environmental requirements of farm animals. Recent research with laying hens has shown that the demand for various floor litters (peat, sand, wood-shavings) is inelastic. Other types of litter (e.g., straw and feathers) are available to laying hens in some housing systems. This study aimed to determine the importance of straw and feathers to laying hens by measuring demand functions for these items. In 1 h sessions individual birds ( n=6) were given the opportunity every second day to work on fixed ratio (FR) schedules (FR5 to FR200) for access to either straw or feathers. The number of responses made and reinforcers delivered was recorded. All birds worked to gain access to straw but only three worked for feathers. None of the hens dustbathed consistently in either litter. The mean elasticities of the demand were significantly different from zero and were −0.48 (s.e. 0.04; p<0.001) for straw and −0.45 (s.e. 0.05; p<0.001) for feathers. The results imply that even if a substrate does not stimulate dustbathing, caged laying hens have a high demand for a litter substrate.

Mean-Variance Utility Functions, Flexible Functional Forms, and the Investment Behaviour of Canadian Life Insurers

This paper models the demand for assets and liabilities by a life insurers. As one step toward the implementation of a utility-dependent portfolio methodology, the paper empirically estimates a family of flexible functional form utility functions (defined over mean and variance). On empirical grounds, in general, the square root quadratic utility function best fits the data. Having determined that utility function the paper then generates estimated mean and variance elasticities for financial assets (liabilities) demand. Broadly speaking, the square root quadratic approximation yields signs for the elasticities of substitution that are consistent with the theory and intuition. The substitutability measures provided (via expected return and variance) among assets within life insurer portfolios provide important information on the impact of regulation of such institutions on their portfolio risk. In addition those measures provide information on the effect of government-induced changes in supply on equilibrium asset yields. Finally, the model also permits a comparison of stock and mutual insurers. The commonly held belief that mutual insurers take a riskier position in the way they discount their business is supported by the results.

Baryon spectra and mean elasticities in proton-nucleus inclusive reactions

A Glauber-type multiple collision model for proton-nucleus inclusive reactions is used in intranuclear cascade calculations to derive the inelastic spectra and the integrated cross section of leadin baryons. Both flat and realistic elasticity distributions are considered in nucleon-nucleon interactions. Model predictions are compared with experimental p-A inclusive cross section data at 100 GeV/c and show satisfactory agreement for a wide range of target nuclei. The dependence of the mean elasticity of the leading nucleon on the final isospin state and on the target mass is also obtained and compared with available data.