Extreme Weights Research Articles

New identities for linearized gravity on the Kerr spacetime

In this paper we derive a differential identity for linearized gravity on the Kerr spacetime and more generally on vacuum spacetimes of Petrov type D. We show that a linear combination of second derivatives of the linearized Weyl tensor can be formed into a complex symmetric 2-tensor $\mathcal{M}_{ab}$ which solves the linearized Einstein equations. The identity makes this manifest by relating $\mathcal{M}_{ab}$ to two terms solving the linearized Einstein equations by construction. The self-dual Weyl curvature of $\mathcal{M}_{ab}$ gives a covariant version of the Teukolsky-Starobinsky identities for linearized gravity which, in addition to the two classical identities for linearized Weyl scalars with extreme spin weights, includes three additional equations. In particular, they are not consequences of the classical Teukolsky-Starobinsky identities, but are additional integrability conditions for linearized gravity. The result has direct application in the construction of symmetry operators and also yields a set of non-trivial gauge invariants for linearized gravity.

Evidence for a perceptual mechanism relating body size misperception and eating disorder symptoms.

There are known and serious health risks associated with extreme body weights, including the development of eating disorders. Body size misperceptions are particularly evident in individuals with eating disorders, compared to healthy controls. The present research investigated whether serial dependence, a recently discovered bias in body size judgement, is associated with eating disorder symptomatology. We additionally examined whether this bias operates on holistic body representations or whether it works by distorting specific visual features. A correlational analysis was used to examine the association between serial dependence and eating disorder symptomatology. We used a within-subjects experimental design to investigate the holistic nature of this misperception. Participants were 63 young women, who judged the size of upright and inverted female body images using a visual analogue scale and then completed the Eating Disorder Examination-Questionnaire (EDE-Q) to assess eating disorder symptoms. Our findings provide the first evidence of an association between serial dependence and eating disorder symptoms, with significant and positive correlations between body size misperception owing to serial dependence and EDE-Q scores, when controlling for Body Mass Index. Furthermore, we reveal that serial dependence is consistent with distortion of local visual features. Findings are discussed in relation to the broader theories of central coherence, cognitive inflexibility, and multisensory integration difficulties, and as providing a candidate mechanism for body size misperception in an eating disorder population. Level 1, experimental study.

Optimal probability weights for estimating causal effects of time-varying treatments with marginal structural Cox models.

Marginal structural Cox models have been used to estimate the causal effect of a time-varying treatment on a survival outcome in the presence of time-dependent confounders. These methods rely on the positivity assumption, which states that the propensity scores are bounded away from zero and one. Practical violations of this assumption are common in longitudinal studies, resulting in extreme weights that may yield erroneous inferences. Truncation, which consists of replacing outlying weights with less extreme ones, is the most common approach to control for extreme weights to date. While truncation reduces the variability in the weights and the consequent sampling variability of the estimator, it can also introduce bias. Instead of truncated weights, we propose using optimal probability weights, defined as those that have a specified variance and the smallest Euclidean distance from the original, untruncated weights. The set of optimal weights is obtained by solving a constrained quadratic optimization problem. The proposed weights are evaluated in a simulation study and applied to the assessment of the effect of treatment on time to death among people in Sweden who live with human immunodeficiency virus and inject drugs.

Application of Luenberger Shortage Function on the Zagreb Stock Exchange: Analysis of Efficient Market Portfolios

In order to apply the CAPM in practice, the estimation of the market portfolio presents one of the biggest challenges. Even more so after the research in early 1990s pointed out the mean-variance inefficiency of stock market capitalization-weighted indices. In the paper we perform an in-sample optimisation for the CROBEX index constituents to test its efficiency ex post. Selected CROBEX index revisions from the period March 2005 – September 2017 are analysed. We find the index to be inefficient which confirms the results of earlier studies. However, since mean-variance optimisation often yields extreme portfolio weights, thus reducing the effective number of stocks in the portfolio, the focus of this research is on testing if improvement in efficiency over the CROBEX index is possible, with respect to the portfolio deconcentration level. The Luenberger’s shortage function is added to the optimisation algorithm in order to increase the number of efficient portfolios analysed.

Vitamin K antagonists and emergencies.

The recent emergence of 'non-VKA' oral anticoagulants may have led to some forgetting that vitamin K antagonists (VKA) are by far the most widely prescribed oral anticoagulants worldwide. Consequently, we decided to summarize the information available on them. This paper presents the problems facing emergency physicians confronted with patients on VKAs in 10 points, from pharmacological data to emergency management. Vitamin K antagonists remain preferable in many situations including in the elderly, in patients with extreme body weights, severe chronic kidney or liver disease or valvular heart disease, and in patients taking VKAs with well-controlled international normalized ratios (INRs). Given the way VKAs work, a stable anticoagulant state can only be achieved at the earliest 5 days after starting therapy. The induction phase of VKA treatment is associated with the highest risk of bleeding; validated algorithms based on INR values have to be followed. VKA asymptomatic overdoses and 'non-severe' hemorrhage are managed by omitting a dose or stopping treatment plus administering vitamin K depending on the INR. Major bleeding is managed using a VKA reversal strategy. A prothrombin complex concentrate infusion plus vitamin K is preferred to rapidly achieve an INR of up to 1.5 and maintain a normal coagulation profile. The INR must be measured 30 min after the infusion. Before an invasive procedure, if an INR of less than 1.5 (<1.3 in neurosurgery) is required, it can be achieved by combining prothrombin complex concentrate and vitamin K. A well-codified strategy is essential for managing patients requiring emergency invasive procedures or presenting bleeding complications.

Causal inference for multi-level treatments with machine-learned propensity scores

Propensity score-based methods have been widely developed to adjust for confounders in observational studies to estimate causal treatment effect for binary treatments. We generalize these causal inference methods to the multi-level treatment case. We review the generalized causal inference framework and several propensity score estimation methods. We conduct a comprehensive simulation study to evaluate the performance of multinomial logistic regression, generalized boosted models, random forest and data adaptive matching score for estimating propensity scores based on inverse probability of treatment weighting. From our findings, multinomial logistic regression is susceptible to yielding extreme weights while a mis-specified model is assumed, which results in poor performance of the inverse probability weighted estimator. On the other hand, machine-learned propensity scores tend to have less biased and more stable performance, and the data adaptive matching score tends to perform the best overall. The above-mentioned propensity score based methods are applied to the Taobao dataset to evaluate the causal effect of reputation on sales.

Extreme Learning Machine Weights Optimization Using Genetic Algorithm In Electrical Load Forecasting

The growth of electrical consumers in Indonesia continues to increases every year, but it is not matched by the provision of adequate infrastructure that available. This causes the available electrical capacity can't fulfill the demand for electricity. In this study, a smart computing system is build to solves the problem. Electrical load data per hour is being used as an input to do the electrical load forecasting with Extreme Learning Machine method. Extreme Learning Machine method uses random input weight within range -1 to 1. Before the electric load prediction process runs, genetic algorithms first optimizing the input weight. According to the test results with weight optimization, MAPE average error rate is 0.799% while without weight optimization the rate rise to 1.1807%. Thus this study implies that Extreme Learning Machine (ELM) method with weight optimization using Genetics Algorithm (GA) can be used in electrical load forecasting problem and give better prediction result

Estimating demand variability and capacity costs due to social network influence: The hidden cost of connection

Widespread access to social networks has led to renewed interest in social network influence in competitive markets. Digital connections enable customers to choose products based not only on intrinsic preferences, but also on inner-circle signals and market share data. However, these influences may significantly increase variability and complexity in demand forecasting. We propose an analytical model to estimate demand based on these three factors of choice. We focus on extreme weights of each factor where the probability distribution is more easily described. Then, we build solution paths as weights depart from the extreme points. We show that beta-binomial distributions can better describe the probability distribution of demand, and provide the parameters of that distribution, for new products helping operations and supply chain managers to take into account risk when making strategic decisions. To the best of our knowledge, we propose the first model that incorporates those three factors of choice in demand forecast. We also explore extreme cases where choice is mostly determined by intrinsic preference rather than social influence, and vice versa.

Pediatric Weight Errors and Resultant Medication Dosing Errors in the Emergency Department

An accurate weight is critical for dosing medications in children. Weight errors can lead to medication-dosing errors. This study examined the frequency and consequences of weight errors occurring at 1 children's hospital and 2 general hospitals. Using an electronic medical record database, 79,000 emergency department encounters of children younger than 5 years were analyzed. Extreme weights were first identified using weight percentiles. Encounters with potential weight errors were further evaluated using a retrospective chart review to determine whether a weight error and medication-dosing error occurred. The percentage of weight errors of total encounters at all 3 institutions was low (0.63% on average), but a large proportion of weight errors led to subsequent medication-dosing errors (34% on average). The children's hospital did not have clinically significantly lower occurrences of weight errors or weight-based medication errors. Common weight errors included the weight in pounds being substituted for the weight in kilograms and decimal placement errors. Weight errors were uncommon at the 3 emergency departments that we studied, but they led to weight-based medication-dosing errors that had the potential to cause harm.

Perinatal outcome of pregnancies complicated with extreme birth weights at term

Objective: The objective of this study is to investigate whether an abnormal birthweight at term, either small for gestational age (SGA, < 5th centile for gestational age) or large for gestational age (LGA, > 95th centile for gestational age), is a risk factor for perinatal complications as compared with birthweight appropriate for gestational age (AGA).Methods: A population-based retrospective cohort analysis of all singleton pregnancies delivered between 1991 and 2014 at Soroka Medical Center. Congenital malformations and multiple pregnancies were excluded. A multivariable generalized estimating equation regression model was used to control for maternal clusters and other confounders.Results: During the study period, 228,242 births met the inclusion criteria, of them 91% were AGA (n = 207,652), 4.7% SGA, and 4.3% LGA. SGA significantly increased the risk for perinatal mortality (aOR 5.6, 95%CI 4.5–6.8) and low 5-min Apgar scores (aOR 2.2, 95%CI 2.0–2.4), while LGA did not. SGA and LGA were both significant risk factors for cesarean delivery. LGA was significantly associated with shoulder dystocia and post-partum hemorrhage (aOR =13.6, 95%CI 10.9–17.0, and aOR 1.7, 95%CI 1.2–2.6, respectively).Conclusions: Extreme birthweights at term are significantly associated with adverse maternal and neonatal outcomes. As opposed to SGA, LGA is not independently associated with perinatal mortality.

Should doses of antibiotics be adjusted?

While we are confronted with the major increase in antibiotic resistance, the preservation of existing antibiotics has become an absolute necessity both to achieve therapeutic success and to limit the risks of the emergence of resistance. The optimization of antibiotic use and dosages must have a threefold objective: guarantee antibacterial efficacy, limit toxicities and limit emergence of resistant strains. However, with the increase in the number of multipathological patients, particularly those with renal or hepatic impairment, the increase in the number of patients with extreme weights and the use of antibiotics with narrower therapeutic margins, the adaptation of antibiotic dosages is becoming increasingly important. By reminding some principles of pharmacokinetics and pharmacodynamics of antibiotics (PK/PD), the necessary objectives for clinical effectiveness of most antibiotic classes are reviewed and several examples of situations where dosage adjustments are necessary will be given. In particular, adjustment of antibiotic dosages in obese patients will be discussed. Adaptation is not limited to the adaptation of the total daily dose. The PK/PD parameters also tell us that the mode of administration (intermittent versus continuous, number of injections per day, etc.) is also an essential point to consider. By taking examples concerning some molecules, infections and difficult clinical situations, we review situations in which dosage adjustments appear necessary.

Ultrasound versus Clinical Examination to Estimate Fetal Weight at Term.

Introduction At term, fetal weight estimation is an important factor for decisions about the delivery mode and the timing of labor induction. This study aimed to compare the accuracy of abdominal palpation with that of ultrasound performed by different examiners to estimate fetal weight. The study investigated whether differences in the examiners' training affected fetal weight estimates. The accuracy of the weight estimates made for fetuses with extreme birth weights was also evaluated. Finally, the accuracy of Johnson's method and of Insler and Bernstein's formula for estimating fetal weight were compared with the other two methods. Methods This prospective study included singleton pregnancies between 37 weeks of gestation and 12 days post-term planned for vaginal delivery or cesarean section. Ultrasound and abdominal palpation using Leopold's maneuvers were performed by examiners with different levels of professional experience. Fetal weight was additionally estimated using Insler and Bernstein's formula and Johnson's method. Statistical analysis calculated the accuracy of fetal weight estimates for the different examiners and the four methods. Results A total of 204 women were included in the analysis. Trained ultrasound examiners were most accurate when estimating fetal weight compared with all other examiners. The comparison of all four methods showed that fetal weight was assessed most accurately with ultrasound. No learning curve could be established. BMI and advanced gestational age affected the accuracy of the estimated weight. The analysis showed that a greater deviation between estimated weight and actual weight occurred with all four methods for fetuses at either end of the extremes of fetal weight, i.e., with very low or very high birth weights. Conclusion Fetal weight should be estimated using ultrasound. A good ultrasound training is essential.

A global optimisation approach to range-restricted survey calibration

Survey calibration methods modify minimally sample weights to satisfy domain-level benchmark constraints (BC), e.g. census totals. This allows exploitation of auxiliary information to improve the representativeness of sample data (addressing coverage limitations, non-response) and the quality of sample-based estimates of population parameters. Calibration methods may fail with samples presenting small/zero counts for some benchmark groups or when range restrictions (RR), such as positivity, are imposed to avoid unrealistic or extreme weights. User-defined modifications of BC/RR performed after encountering non-convergence allow little control on the solution, and penalisation approaches modelling infeasibility may not guarantee convergence. Paradoxically, this has led to underuse in calibration of highly disaggregated information, when available. We present an always-convergent flexible two-step global optimisation (GO) survey calibration approach. The feasibility of the calibration problem is assessed, and automatically controlled minimum errors in BC or changes in RR are allowed to guarantee convergence in advance, while preserving the good properties of calibration estimators. Modelling alternatives under different scenarios using various error/change and distance measures are formulated and discussed. The GO approach is validated by calibrating the weights of the 2012 Health Survey for England to a fine age–gender–region cross-tabulation (378 counts) from the 2011 Census in England and Wales.

Modelling Equitable and Reasonable Water Sharing in Transboundary Rivers: the Case of Sirwan-Diyala River

There are over 260 transboundary river and lake basins in the world that many of them are facing great challenges of water sharing between riparian countries concerned. The 1997 UN Watercourses Convention, entered into force in 2014, includes articles and factors on water sharing which have not been completely used for modelling of the basins yet. In this paper, legal aspects (i.e. Articles 5, 6, 7 and 10 of the Convention) are integrated with a technical approach for water allocation in transboundary rivers. For this purpose, a new conceptual model is developed for quantification of the Convention provisions concerning equitable and reasonable water sharing. The method is applied to the Sirwan-Diyala transboundary river shared by Iran and Iraq. Some indicators are developed and quantified for determination of water shares of the riparian countries and different scenarios considering extreme and equal weights of the factors are defined. The basin is simulated by WEAP model to evaluate effects of the scenarios on up- and downstream of the basin. Five demand management alternatives comprising increasing of irrigation efficiency and eliminating second cultivation are proposed as appropriate measures for elimination or mitigation of possible significant harm. The proposed technical-legal approach paves the way for enhancing bargaining potentials of the riparian countries and increasing their cooperation to achieve a win-win solution in using waters of transboundary rivers.

The Association of Birth Weight and Infant Growth with Energy Balance-Related Behavior - A Systematic Review and Best-Evidence Synthesis of Human Studies.

BackgroundSuboptimal prenatal and early postnatal growths are associated with obesity in later life, but the underlying mechanisms are unknown. The aim of this study was to systematically review the literature that reports on the longitudinal association of (i) birth size or (ii) infant growth with later (i) energy intake, (ii) eating behaviors, (iii) physical activity or (iv) sedentary behavior in humans.MethodsA comprehensive search of MEDLINE, EMBASE, PsycINFO and The Cochrane Library was conducted to identify relevant publications. We appraised the methodological quality of the studies and synthesized the extracted data through a best-evidence synthesis.ResultsData from 41 publications were included. The quality of the studies was high in three papers, moderate in 11 and low in the large majority (n = 27) of papers appraised. Our best-evidence synthesis indicates that there is no evidence for an association of birth weight with later energy intake, eating behavior, physical activity or sedentary behavior. We found moderate evidence for an association of extreme birth weights (at both ends of the spectrum) with lower physical activity levels at a later age. Evidence for the association of infant growth with energy balance-related behavior was generally insufficient.ConclusionsWe conclude that current evidence does not support an association of early-life growth with energy balance-related behaviors in later life, except for an association of extreme birth weights with later physical activity.

Topological Distances Between Brain Networks.

Many existing brain network distances are based on matrix norms. The element-wise differences may fail to capture underlying topological differences. Further, matrix norms are sensitive to outliers. A few extreme edge weights may severely affect the distance. Thus it is necessary to develop network distances that recognize topology. In this paper, we introduce Gromov-Hausdorff (GH) and Kolmogorov-Smirnov (KS) distances. GH-distance is often used in persistent homology based brain network models. The superior performance of KS-distance is contrasted against matrix norms and GH-distance in random network simulations with the ground truths. The KS-distance is then applied in characterizing the multimodal MRI and DTI study of maltreated children.

Safety of Doacs in Patients of Extreme Weight

▪Direct Oral Anticoagulants (DOACs), specifically factor Xa inhibitors, have been approved for VTE treatment, VTE prophylaxis after hip and knee replacement, and stroke prevention in non-valvular atrial fibrillation. The DOACs are fast replacing warfarin for these indications due to their ease of administration, fixed dosing, and fast onset and offset of action. However, there are no specific dosing recommendations for DOACs in patient with extreme body weight because these agents were not well represented in the clinical trials, and no specific trials examining safety or efficacy in patients of extreme weight have been conducted. A recent analysis of clinical trials data by the ISTH suggests that while data is limited, the available data suggests that DOACs are safe in patients less than 120 kg at standard doses, and are not recommended in patients greater than 120 kg unless specific concentration levels are obtained to assess their efficacy.To better understand the safety of DOACs in patients of extreme weights, we performed a retrospective analysis of a random sample of patients of low weight (<60 kg), normal weight (60-120 kg), and extreme weight (>120 kg). A random sample of 113 charts was extracted from the medical record; 34 patients were excluded due to missing data, and 79 patients were included with 27 in the <60 kg group, and 26 in both the normal and obese weight groups. Data was collected on patients from May 2011 through April 2016. Baseline patient characteristics, bleeding events, documented clot progression, and several laboratory values (hemoglobin, platelet count, creatinine and INR at commencement of anticoagulation, hemoglobin and INR at discharge or closest follow up appointment) were recorded. The outcomes assessed were rates of bleeding and clot progression.Thirty-five (44.30%) patients were male. The average age in each group was 64, 65, and 64, respectively. Forty-eight (60.76%) patients received apixaban, and the remaining patients were given rivaroxaban. Thirty-six (45.57%) patients received anticoagulation for atrial fibrillation, 26 (32.91%) had deep vein thrombosis, 13 (16.46%) had pulmonary embolism, and 4 (5.06%) had other reasons, such as peripheral arterial disease or arterial thrombus. In the low weight group, 9 patients had a documented bleeding episode (33.33%, p=0.1289), versus 4 patients in the normal weight group (15.38%) and 9 patients in the overweight group (27.85%, p=0.1091). There was no major bleeding in patients of normal weight but bleeding occurred in 4 in the underweight group 14.81%, p=.0413) and 3 in the overweight group (11.54%, p=.0744). In total, 22 of 79 patients (27.85%) had a bleeding episode. Two patients in the underweight group had clot progression (7.41%, p=0.9681), versus 2 patients in the normal weight group and no patients in the overweight group. There was no significant difference between patients who bled and those who did not bleed in creatinine, hemoglobin, platelet count or INR at the time of initiation of DOAC. We did not find a significant difference in rates of bleeding in low weight or overweight patients when compared to normal weight individuals; however there was a trend toward significance in both groups. Patients received either 5 mg bid of apixaban or 20 mg daily of rivaroxaban in both groups, therefore the difference was not attributable to different prescribing patterns. Neither group had a significant number of patients with clot progression. It is intriguing that both low weight and overweight patients had similar rates of bleeding (33.33 and 34.62%, respectively).The PK/PD data referenced by the ISTH raised the concern that overweight patients may actually be underdosed if given standard doses of DOACs. Our data, though limited by the small number of patients, poses very interesting and clinically relevant questions about DOAC use in both weight extremes: are we overdosing DOACs for underweight patients? Why are overweight patients bleeding at similar rates? We plan on formulating a prospective study to answer these questions, utilizing drug-specific peak and trough levels to ascertain sub-, supra-, and therapeutic levels in patients who bleed on DOAC therapy. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Computed tomography protocols used in staging bronchopulmonary carcinoma: Results of a national survey

ObjectivesTo know the protocols used for staging bronchopulmonary carcinoma by computed tomography in Spain. Material and methodsRadiologists in 129 hospitals were sent email questionnaires about the organization of their department, scanner type and manufacturer, study extension, techniques employed, and protocol for administering contrast material. ResultsA total of 109 hospitals responded with data from 91 teams. Most hospitals were affiliated with a university, and most departments were organized by organ-systems. Scanners were from four manufacturers, and 68% had either 16 or 64 detectors. In 61% of the hospitals, the dose of contrast agent is modified only in patients with extreme body weights, and in 22% the dose is not individualized. Most hospitals do contrast-enhanced studies of the chest and upper abdomen, 42.4% through a single thoracoabdominal acquisition and 55.9% through independent chest and abdominal acquisitions; there was a significant association between these approaches and the scanner manufacturer's protocols and whether the hospital was affiliated with a university. The most commonly used technical parameters were 120kV with dose modulation and variable milliamperage. ConclusionThere is very little variability among hospitals in the type of scanner used, the study extension, and the technical parameters used to stage bronchopulmonary carcinoma. Most centers individualize the dose of contrast agent only in extreme weights. There is a broad division between using one or two acquisitions to image the thorax and abdomen, and the number of acquisitions is related to the scanner manufacturer and whether the hospital is affiliated with a university.

Protocolos de tomografía computarizada empleados en la estadificación del carcinoma broncopulmonar: resultados de una encuesta a nivel nacional

ObjectivesTo know the protocols used for staging bronchopulmonary carcinoma by computed tomography in Spain. Material and methodsRadiologists in 129 hospitals were sent email questionnaires about the organization of their department, scanner type and manufacturer, study extension, techniques employed, and protocol for administering contrast material. ResultsA total of 109 hospitals responded with data from 91 teams. Most hospitals were affiliated with a university, and most departments were organized by organ-systems. Scanners were from four manufacturers, and 68% had either 16 or 64 detectors. In 61% of the hospitals, the dose of contrast agent is modified only in patients with extreme body weights, and in 22% the dose is not individualized. Most hospitals do contrast-enhanced studies of the chest and upper abdomen, 42.4% through a single thoracoabdominal acquisition and 55.9% through independent chest and abdominal acquisitions; there was a significant association between these approaches and the scanner manufacturer's protocols and whether the hospital was affiliated with a university. The most commonly used technical parameters were 120kV with dose modulation and variable milliamperage. ConclusionThere is very little variability among hospitals in the type of scanner used, the study extension, and the technical parameters used to stage bronchopulmonary carcinoma. Most centers individualize the dose of contrast agent only in extreme weights. There is a broad division between using one or two acquisitions to image the thorax and abdomen, and the number of acquisitions is related to the scanner manufacturer and whether the hospital is affiliated with a university.

Portfolio selection with conservative short-selling

Mean-variance analysis is considered the foundation of portfolio selection. Among various attempts to address the limitations of the original model as formulated by Markowitz more than 60 years ago, one simple solution has been to impose constraints on weights in order to reduce efficient portfolios with extreme weights that may be caused by estimation errors in the inputs. Although no short-selling constraints are often considered, the restriction removes opportunities to gain from short-selling and short positions provide various investment opportunities such as long/short strategies. In this paper we propose a portfolio selection model that allows short positions while examining the worst case only for assets that are assigned negative weights. The proposed model constructs portfolios with conservative short positions and the conservative level can be adjusted by the investor.