503 results on '"Crossover"'
Search Results
2. Prevalence and Impact of Treatment Crossover in Cardiac Surgery Randomized Trials: A Meta‐Epidemiologic Study
- Author
-
Mario Gaudino, Stephen E. Fremes, Marc Ruel, Antonino Di Franco, Michele Di Mauro, Joanna Chikwe, Giacomo Frati, Leonard N. Girardi, David P. Taggart, and Giuseppe Biondi‐Zoccai
- Subjects
cardiac surgery ,crossover ,meta‐epidemiologic study ,randomized controlled trial ,surgery ,Diseases of the circulatory (Cardiovascular) system ,RC666-701 - Abstract
Background Crossover dilutes treatment effect and reduces statistical power of intention‐to‐treat analysis. We examined incidence and impact on cardiac surgery randomized controlled trial (RCT) outcomes of crossover from experimental to control interventions, or vice versa. Methods and Results MEDLINE, EMBASE, and Cochrane Library were searched, and RCTs (≥100 patients) comparing ≥2 adult cardiac surgical interventions were included. Crossover from the initial treatment assignment and relative risks (RRs) for each trial's primary end point and mortality at longest available follow‐up were extracted. All RRs were calculated as >1 favored control group and
- Published
- 2019
- Full Text
- View/download PDF
3. <scp>H3K9</scp> demethylases <scp>IBM1</scp> and <scp>JMJ27</scp> are required for male meiosis in Arabidopsis thaliana
- Author
-
Jinping Cheng, Linhao Xu, Valentin Bergér, Astrid Bruckmann, Chao Yang, Veit Schubert, Klaus D. Grasser, Arp Schnittger, Binglian Zheng, and Hua Jiang
- Subjects
Histones ,Mammals ,Jumonji Domain-Containing Histone Demethylases ,Meiosis ,Arabidopsis Proteins ,Physiology ,Arabidopsis ,Animals ,epigenetics ,meiosis ,H3K9me2 ,crossover ,histone modification ,Arabidopsis thaliana ,Plant Science - Abstract
Dimethylation of histone H3 lysine 9 (H3K9me2), a crucial modification for heterochromatin formation and transcriptional silencing, is essential for proper meiotic prophase progression in mammals. We analyzed meiotic defects and generated genome-wide profiles of H3K9me2 and transcriptomes for the mutants of H3K9 demethylases. Moreover, we also identified proteins interacting with H3K9 demethylases. H3K9me2 is usually found at transposable elements and repetitive sequences but is absent from the bodies of protein-coding genes. In this study, we show that the Arabidopsis thaliana H3K9 demethylases IBM1 and JMJ27 cooperatively regulate crossover formation and chromosome segregation. They protect thousands of protein-coding genes from ectopic H3K9me2, including genes essential for meiotic prophase progression. In addition to removing H3K9me2, IBM1 and JMJ27 interact with the Precocious Dissociation of Sisters 5 (PDS5) cohesin complex cofactors. The pds5 mutant shared similar transcriptional alterations with ibm1 jmj27, including meiosis-essential genes, yet without affecting H3K9me2 levels. Hence, PDS5s, together with IBM1 and JMJ27, regulate male meiosis and gene expression independently of H3K9 demethylation. These findings uncover a novel role of H3K9me2 removal in meiosis and a new function of H3K9 demethylases and cohesin cofactors in meiotic transcriptional regulation.
- Published
- 2022
4. An Olefinic 1, <scp> 2‐ α ‐Boryl </scp> Migration Enables 1, <scp>2‐Bis</scp> (boronic esters) via <scp>Radical‐Polar</scp> Crossover Reaction
- Author
-
Kai Yang, Feng Zhang, Qiuling Song, Chenglan Wang, Cece Wang, Lu Zhou, Shangteng Liao, and Yixian Lou
- Subjects
Chemistry ,Crossover ,Polymer chemistry ,Polar ,General Chemistry - Published
- 2022
5. High utility itemset mining using genetic algorithm assimilated with off policy reinforcement learning to adaptively calibrate crossover operation
- Author
-
P Suresh and K Logeswaran
- Subjects
Computational Mathematics ,Artificial Intelligence ,Computer science ,business.industry ,Genetic algorithm ,Crossover ,Reinforcement learning ,Artificial intelligence ,business ,Evolutionary computation - Published
- 2021
6. Compact filtering crossover design based on <scp>SIW quintuple‐mode</scp> resonators
- Author
-
Huaishu Jing, Yonghong Zhang, Yong Fan, Jiawei Liu, and Lili Qu
- Subjects
Resonator ,Materials science ,Crossover ,Mode (statistics) ,Electrical and Electronic Engineering ,Condensed Matter Physics ,Topology ,Crossover study ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials - Published
- 2021
7. A Perspective of Antennas for 5G and 6G
- Author
-
Yingjie Jay Guo and Richard W. Ziolkowski
- Subjects
Antenna array ,Beamforming ,business.industry ,Computer science ,Perspective (graphical) ,Crossover ,Electronic engineering ,Wireless ,Antenna (radio) ,business ,5G ,Power (physics) - Abstract
At the core of wireless devices, systems, networks, and ecosystems are their antennas and antenna arrays. To achieve the many stunning and amazing 5G and 6G promises, significant advances in antenna and antenna array technologies must be accomplished. Desirable integrated space and terrestrial network features pose a number of significant and interesting challenges for future 6G antennas and antenna arrays. There are several ways to form multiple beams from an array. Major schemes can be categorized into digital, analog, and crossover strategies. This chapter describes digital beamforming and a major crossover of much recent excitement, hybrid beamforming. High‐gain antenna arrays are even more necessary for anticipated 6G operations. Other important related THz technologies that must be developed to address 6G expectations are high power sources and highly sensitive receivers. The chapter discusses the concept of single input and multiple output and multiple input and multiple output multi‐beam antennas.
- Published
- 2021
8. Sulfonated Cellulose Membranes Improve the Stability of Aqueous Organic Redox Flow Batteries
- Abstract
The drawbacks of current state-of-the-art selective membranes, such as poor barrier properties, high cost, and poor recyclability, limit the large-scale deployment of electrochemical energy devices such as redox flow batteries (RFBs) and fuel cells. In recent years, cellulosic nanomaterials have been proposed as a low-cost and green raw material for such membranes, but their performance in RFBs and fuel cells is typically poorer than that of the sulfonated fluoropolymer ionomer membranes such as Nafion. Herein, sulfonated cellulose nanofibrils densely cross-linked to form a compact sulfonated cellulose membrane with limited swelling and good stability in water are used. The membranes possess low porosity and excellent ionic transport properties. A model aqueous organic redox flow battery (AORFB) with alizarin red S as negolyte and tiron as posolyte is assembled with the sulfonated cellulose membrane. The performance of the nanocellulose-based battery is superior in terms of cyclability in comparison to that displayed by the battery assembled with commercially available Nafion 115 due to the mitigation of crossover of the redox-active components. This finding paves the way to new green organic materials for fully sustainable AORFB solutions., QC 20230908
- Published
- 2022
- Full Text
- View/download PDF
9. Crossover between the control of fungal pathogens in medicine and the wider environment, and the threat of antifungal resistance
- Author
-
Ulrich Gisi
- Subjects
Antifungal ,Resistance (ecology) ,medicine.drug_class ,Crossover ,Genetics ,medicine ,Plant Science ,Horticulture ,Biology ,Agronomy and Crop Science ,Microbiology - Published
- 2021
10. Surfactant head group and concentration influence on structure and dynamics of gellan gum hydrogels: Crossover from stretched to compressed exponential
- Author
-
Sidhartha S. Jena and K Mithra
- Subjects
Materials science ,Polymers and Plastics ,Crossover ,Gellan gum ,Exponential function ,chemistry.chemical_compound ,Dynamic light scattering ,Pulmonary surfactant ,Chemical engineering ,Rheology ,chemistry ,Self-healing hydrogels ,Materials Chemistry ,Head (vessel) ,Physical and Theoretical Chemistry - Published
- 2021
11. It takes a village: How organizational support for adoption positively affects employees and their families
- Author
-
Matthew J. Quade, Ryan P. Hanlon, Dawn S. Carlson, and Kaylee J. Hackney
- Subjects
Organizational Behavior and Human Resource Management ,Work (electrical) ,Spillover effect ,Crossover ,Demographic economics ,Psychology ,Applied Psychology - Published
- 2021
12. Combining Business Law with Business Theory: An Experiential Classroom Crossover Activity
- Author
-
Kimberly Roush, Matt Roessing, Justin Roush, and Jehan El-Jourbagy
- Subjects
Crossover ,Mathematics education ,Commercial law ,Sociology ,Experiential learning - Published
- 2021
13. Crossover of daily job stressors among dual‐career couples: A dyadic examination
- Author
-
Allison M. Ellis and Zheng Chen
- Subjects
Organizational Behavior and Human Resource Management ,Sociology and Political Science ,Stressor ,Crossover ,DUAL (cognitive architecture) ,Psychology ,General Psychology ,Applied Psychology ,Developmental psychology - Published
- 2021
14. Visible Light Assisted Radical‐Polar/Polar‐Radical Crossover Reactions in Organic Synthesis
- Author
-
Shivani Sharma, Anuj Sharma, and Jitender Singh
- Subjects
chemistry.chemical_compound ,Chemistry ,Crossover ,Reactive intermediate ,Photocatalysis ,Polar ,Organic synthesis ,General Chemistry ,Photochemistry ,Visible spectrum - Published
- 2021
15. Impact of study design and statistical model in pharmacogenetic studies with gene‐treatment interaction
- Author
-
France Mentré, Julie Bertrand, and Camille Couffignal
- Subjects
Genotype ,Computer science ,Clinical Decision-Making ,Crossover ,RM1-950 ,Computational biology ,Interaction ,Article ,Humans ,Computer Simulation ,Drug Interactions ,Pharmacology (medical) ,Gene ,Melatonin ,Treatment interaction ,Clinical Trials as Topic ,Cross-Over Studies ,Models, Statistical ,Polymorphism, Genetic ,Receptor, Melatonin, MT2 ,Research ,Statistical model ,Articles ,Genetic Therapy ,Pharmacogenomic Testing ,Clinical trial ,Cytochrome P-450 CYP2D6 ,Modeling and Simulation ,Cytochrome P-450 CYP3A Inhibitors ,Dopamine Antagonists ,Haloperidol ,Therapeutics. Pharmacology ,Gene polymorphism ,Itraconazole ,Algorithms ,Pharmacogenetics - Abstract
Gene‐treatment interactions, just like drug‐drug interactions, can have dramatic effects on a patient response and therefore influence the clinician decision at the patient’s bedside. Crossover designs, although they are known to decrease the number of subjects in drug‐interaction studies, are seldom used in pharmacogenetic studies. We propose to evaluate, via realistic clinical trial simulations, to what extent crossover designs can help quantifying the gene‐treatment interaction effect. We explored different scenarios of crossover and parallel design studies comparing two symptom‐modifying treatments in a chronic and stable disease accounting for the impact of a one gene and one gene‐treatment interaction. We varied the number of subjects, the between and within subject variabilities, the gene polymorphism frequency and the effect sizes of the treatment, gene, and gene‐treatment interaction. Each simulated dataset was analyzed using three models: (i) estimating only the treatment effect, (ii) estimating the treatment and the gene effects, and (iii) estimating the treatment, the gene, and the gene‐treatment interaction effects. We showed how ignoring the gene‐treatment interaction results in the wrong treatment effect estimates. We also highlighted how crossover studies are more powerful to detect a treatment effect in the presence of a gene‐treatment interaction and more often lead to correct treatment attribution.
- Published
- 2021
16. Power and sample size for <scp>GEE</scp> analysis of incomplete paired outcomes in 2 × 2 crossover trials
- Author
-
Yongqiang Tang
- Subjects
Pharmacology ,Statistics and Probability ,Cross-Over Studies ,Models, Statistical ,Binomial regression ,Crossover ,Variance (accounting) ,Bivariate analysis ,Missing data ,01 natural sciences ,Gee ,010104 statistics & probability ,03 medical and health sciences ,0302 clinical medicine ,Research Design ,Sample size determination ,Sample Size ,Statistics ,Humans ,Computer Simulation ,Pharmacology (medical) ,030212 general & internal medicine ,0101 mathematics ,Generalized estimating equation ,Mathematics - Abstract
The 2 × 2 crossover trial uses subjects as their own control to reduce the intersubject variability in the treatment comparison, and typically requires fewer subjects than a parallel design. The generalized estimating equations (GEE) methodology has been commonly used to analyze incomplete discrete outcomes from crossover trials. We propose a unified approach to the power and sample size determination for the Wald Z-test and t-test from GEE analysis of paired binary, ordinal and count outcomes in crossover trials. The proposed method allows misspecification of the variance and correlation of the outcomes, missing outcomes, and adjustment for the period effect. We demonstrate that misspecification of the working variance and correlation functions leads to no or minimal efficiency loss in GEE analysis of paired outcomes. In general, GEE requires the assumption of missing completely at random. For bivariate binary outcomes, we show by simulation that the GEE estimate is asymptotically unbiased or only minimally biased, and the proposed sample size method is suitable under missing at random (MAR) if the working correlation is correctly specified. The performance of the proposed method is illustrated with several numerical examples. Adaption of the method to other paired outcomes is discussed.
- Published
- 2021
17. Suppressing the liquid product crossover in electrochemical CO2 reduction
- Author
-
David Sinton, Alexander H. Ip, Geonhui Lee, Ning Wang, Alberto Vomiero, Edward H. Sargent, Rui Kai Miao, and Hongyan Liang
- Subjects
Liquid product ,Reduction (complexity) ,bipolar membranes ,Materials science ,Chemical engineering ,CO2 reduction ,Crossover ,TA401-492 ,solid‐state electrolytes ,Solid state electrolyte ,Electrochemistry ,liquid product crossover ,Materials of engineering and construction. Mechanics of materials - Abstract
Coupling electrochemical CO2 reduction (CO2R) with a renewable energy source to create high‐value fuels and chemicals is a promising strategy in moving toward a sustainable global energy economy. CO2R liquid products, such as formate, acetate, ethanol, and propanol, offer high volumetric energy density and are more easily stored and transported than their gaseous counterparts. However, a significant amount (~30%) of liquid products from electrochemical CO2R in a flow cell reactor cross the ion exchange membrane, leading to the substantial loss of system‐level Faradaic efficiency. This severe crossover of the liquid product has—until now—received limited attention. Here, we review promising methods to suppress liquid product crossover, including the use of bipolar membranes, solid‐state electrolytes, and cation‐exchange membranes‐based acidic CO2R systems. We then outline the remaining challenges and future prospects for the production of concentrated liquid products from CO2.
- Published
- 2021
18. For better or for worse family‐related well‐being: A meta‐analysis of crossover effects in dyadic studies
- Author
-
Laurenţiu P. Maricuțoiu, Delia Vîrgă, and Alina Matei
- Subjects
Cross-Over Studies ,030505 public health ,Yield (finance) ,05 social sciences ,Crossover ,050109 social psychology ,Crossover effects ,Variance (accounting) ,Structural equation modeling ,03 medical and health sciences ,Spillover effect ,Surveys and Questionnaires ,Meta-analysis ,Well-being ,Statistics ,Humans ,Family ,0501 psychology and cognitive sciences ,0305 other medical science ,Psychology ,Applied Psychology - Abstract
The present preregistered meta-analysis aimed to assess the evidence regarding the work-family interactions, as dyadic studies report them. The introduction differentiated between spillover (or intra-individual) effects and crossover (or inter-individual) effects by using dyadic studies. Following an online and reference list search, out of the initial 339 studies, 36 eligible articles reported correlations between one partner's variables and the other partner's variables. Analyses included 1504 effect sizes and used meta-analytical calculations and structural equation modeling. Both partners' well-being measures had small proportions of shared variance (i.e. shared variance up to 13.69%). The following analyses focused on the potential effects that could explain the shared variance of family-related well-being. There was little evidence of a crossover effect from one's work-related variables toward the partners' family-related well-being. Furthermore, analyses using structural equation modeling did not yield any results to support a crossover effect from one's work-family interaction toward their partner's well-being. These findings suggest that the literature needs new research studies regarding how family-related demands and resources are related to well-being and personal resources in the crossover processes.
- Published
- 2021
19. Design of a NATM crossover at Mumbai metro line 3
- Author
-
Jitendra Manvani, Florian Krenn, Prathap Muniyappa, and Akshay Panwar
- Subjects
Rock mechanics ,business.industry ,Computer science ,Crossover ,Structural engineering ,New Austrian Tunnelling method ,Line (text file) ,Geotechnical Engineering and Engineering Geology ,business ,Crossover study ,Urban environment ,Civil and Structural Engineering - Published
- 2020
20. Stimulation Parameters for Sacral Neuromodulation on Lower Urinary Tract and Bowel Dysfunction-Related Clinical Outcome
- Subjects
SYMPTOMS ,FECAL INCONTINENCE ,VOIDING DYSFUNCTION ,MULTICENTER ,sacral nerve stimulation ,CROSSOVER ,stimulation paradigm ,EFFICACY ,NERVE-STIMULATION ,THERAPY ,TERM-FOLLOW-UP ,THRESHOLD - Abstract
Objective Sacral neuromodulation (SNM) has been used to treat patients with lower urinary tract dysfunction and bowel dysfunction for many years. Success rates vary between 50% and 80%, indicating that there is much room for improvement. Altering stimulation parameters may result in improved outcome. This paper reports a systematic review of the clinical efficacy of nonconventional stimulation parameters on urinary tract and bowel dysfunction. Materials and Methods Three databases were used for the literature search: Ovid (Medline, Embase) and PubMed. Papers were screened by two independent reviewers, who also extracted data from these papers. Clinical papers studying SNM stimulation parameters, that is, intermittent stimulation, frequency, pulse width, and amplitude, in urinary tract and bowel dysfunction were included. Quality of included papers was assessed using standardized guidelines. Results Out of 5659 screened papers, 17 papers, studying various stimulation parameters, were included. Overall quality of these papers differed greatly, as some showed no risk of bias, whereas others showed high risk of bias. Stimulation parameters included intermittent stimulation, frequency, pulse width, amplitude, and unilateral vs. bilateral stimulation. Especially high frequency SNM and either a narrow or wide pulse width seem to improve efficacy in patients with bowel dysfunction. Additionally, implementation of short cycling intervals is promising to improve quality of life for patients with urinary tract or bowel dysfunction. Conclusion The results of our systematic review indicate that stimulation parameters may improve efficacy of SNM in treatment of both urinary tract dysfunction and bowel dysfunction.
- Published
- 2020
21. Multi‐objective design of energy harvesting enabled wireless networks based on evolutionary genetic optimisation
- Author
-
Ridhima Mehta
- Subjects
Control and Optimization ,Computer Networks and Communications ,Computer science ,Heuristic (computer science) ,Distributed computing ,Crossover ,02 engineering and technology ,TK5101-6720 ,Management Science and Operations Research ,01 natural sciences ,Evolutionary computation ,Genetic algorithm ,evolutionary genetic optimisation ,0202 electrical engineering, electronic engineering, information engineering ,Wireless ,energy‐restrained wireless network services ,energy efficiency ,energy conservation ,business.industry ,Wireless network ,010401 analytical chemistry ,020206 networking & telecommunications ,0104 chemical sciences ,Energy conservation ,spectrum outage ,genetic optimisation model ,Telecommunication ,business ,Efficient energy use - Abstract
Sustainable operation of energy-restrained wireless network services requires multiple objectives to be satisfied synchronously. Among these objectives, reduced spectrum outage, energy conservation, and minimal packet transmission failures considerably affect the energy harvesting operation of these networks. These three objectives are associated with disparate protocol layers incorporating the transport, medium access control, and physical layers of traditional networking architecture. The authors investigate energy harvesting wireless communications by formulating the multi-objective optimisation problem comprising these global networking criteria, which are simultaneously optimised with the heuristic design procedure. For this, they employ a Pareto-based evolutionary genetic algorithm technique built in the wireless network design and operation to find the optimal set of all non-dominated solutions traversing the entire design search space. Besides, iterative implementation of the presented genetic optimisation model with distinct feasible integrations of crossover and mutation operations is performed to evaluate the proficiency of the proposed scheme for evaluating the Pareto-optimal frontier set. The influence of different combinations of these operations is examined and adaptively applied with appropriate genetic parameters tuning for efficient meta-heuristic search through the candidate solution space. Simulation results demonstrate that the proposed hybrid genetic mechanism outperforms the existing methods in terms of throughput, energy efficiency, and loss rate.
- Published
- 2020
22. Analysis of crossover designs with nonignorable dropout
- Author
-
Vernon M. Chinchilli and Xi Wang
- Subjects
Statistics and Probability ,Mathematical optimization ,Patient Dropouts ,Epidemiology ,Computer science ,Crossover ,01 natural sciences ,010104 statistics & probability ,03 medical and health sciences ,0302 clinical medicine ,Software ,Robustness (computer science) ,Humans ,Longitudinal Studies ,030212 general & internal medicine ,0101 mathematics ,Probability ,Cross-Over Studies ,Models, Statistical ,Binary outcome ,business.industry ,Estimation theory ,Conditional probability distribution ,Missing data ,Discrete time and continuous time ,Linear Models ,business - Abstract
This article addresses the analysis of crossover designs with nonignorable dropout. We study nonreplicated crossover designs and replicated designs separately. With a primary objective of comparing the treatment mean effects, we jointly model the longitudinal measures and discrete time to dropout. We propose shared-parameter models and mixed-effects selection models. We adapt a linear-mixed effects model as the conditional model for the longitudinal outcomes. We invoke a discrete-time hazards model with a complementary log-log link function for the conditional distribution of time to dropout. We apply maximum likelihood for parameter estimation. We perform simulation studies to investigate the robustness of our proposed approaches under various missing data mechanisms. We then apply the approaches to two examples with a continuous outcome and one example with a binary outcome using existing software. We also implement the controlled multiple imputation methods as a sensitivity analysis of the missing data assumption.
- Published
- 2020
23. An iterative method to protect the type I error rate in bioequivalence studies under two‐stage adaptive 2×2 crossover designs
- Author
-
Detlew Labes, Eduard Molins, Helmut Schütz, Erik Cobo, Jordi Ocaña, Universitat Politècnica de Catalunya. Doctorat en Estadística i Investigació Operativa, Universitat Politècnica de Catalunya. Departament d'Estadística i Investigació Operativa, and Universitat Politècnica de Catalunya. GRBIO - Grup de Recerca en Bioestadística i Bioinformàtica
- Subjects
Statistics and Probability ,Biomatemàtica ,Computer science ,Iterative method ,Crossover ,Matemàtiques i estadística::Matemàtica aplicada a les ciències [Àrees temàtiques de la UPC] ,Value (computer science) ,significance level adjustment ,Bioequivalence ,01 natural sciences ,two-stage adaptive designs (TSD) ,010104 statistics & probability ,03 medical and health sciences ,0302 clinical medicine ,Generic drug ,Interim ,Statistics ,Humans ,030212 general & internal medicine ,0101 mathematics ,Set (psychology) ,Biomathematics ,Cross-Over Studies ,generic drug product ,92 Biology and other natural sciences::92B Mathematical biology in general [Classificació AMS] ,type I error control (T1E) ,General Medicine ,Average bioequivalence (ABE) ,Therapeutic Equivalency ,Research Design ,Sample Size ,Statistics, Probability and Uncertainty ,Type I and type II errors - Abstract
This is the peer reviewed version of the following article: Molins, E. [et al.]. An iterative method to protect the type I error rate in bioequivalence studies under two-stage adaptive 2×2 crossover designs. "Biometrical journal", 2021, vol. 63, núm. 1, p. 122-133., which has been published in final form at https://onlinelibrary.wiley.com/doi/10.1002/bimj.201900388. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. Bioequivalence studies are the pivotal clinical trials submitted to regulatory agen- cies to support the marketing applications of generic drug products. Average bioequivalence (ABE) is used to determine whether the mean values for the pharmacokinetic measures determined after administration of the test and refer- ence products are comparable. Two-stage 2×2 crossover adaptive designs (TSDs) are becoming increasingly popular because they allow making assumptions on the clinically meaningful treatment effect and a reliable guess for the unknown within-subject variability. At an interim look, if ABE is not declared with an ini- tial sample size, they allow to increase it depending on the estimated variability and to enroll additional subjects at a second stage, or to stop for futility in case of poor likelihood of bioequivalence. This is crucial because both parameters must clearly be prespecified in protocols, and the strategy agreed with regulatory agen- cies in advance with emphasis on controlling the overall type I error. We present an iterative method to adjust the significance levels at each stage which preserves the overall type I error for a wide set of scenarios which should include the true unknown variability value. Simulations showed adjusted signif- icance levels higher than 0.0300 in most cases with type I error always below 5%, and with a power of at least 80%. TSDs work particularly well for coefficients of variation below 0.3 which are especially useful due to the balance between the power and the percentage of studies proceeding to stage 2. Our approach might support discussions with regulatory agencies. This research is partially supported by the grant MTM2015-64465-C2-1-R (MINECO/FEDER) from the Ministerio de Economia y Competitividad (Spain) and by the grant 2014 SGR 464 from the Generalitat de Catalunya.
- Published
- 2020
24. Seed picking crossover optimisation algorithm for semantic segmentation from images
- Author
-
Vijayakumari Pushparaj and Manonmani Arunkumar
- Subjects
Conditional random field ,Iterative method ,Computer science ,Crossover ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,segmented regions ,object recognition ,QA76.75-76.765 ,Photography ,Segmentation ,Optimisation algorithm ,visually uniform regions ,Computer software ,Electrical and Electronic Engineering ,TR1-1050 ,Contextual image classification ,business.industry ,Cognitive neuroscience of visual object recognition ,Pattern recognition ,Image segmentation ,semantic image segmentation ,partitioned regions ,Signal Processing ,Computer Vision and Pattern Recognition ,Artificial intelligence ,pixel classification ,business ,Software - Abstract
Semantic image segmentation treats the issues involved in the object recognition and image segmentation as a combined task. The chief notion of semantic segmentation is to partition the image into visually uniform regions and to discriminate the class of the partitioned regions. Pixel classification is done over the segmented regions by assigning semantic labels. In general, inference frameworks are fed with the combination of low‐level features and high‐level contextual cues to segment an image. Since these combinations are rarely object consistent, result with minimum classification accuracy because of choosing non‐influencing features and cues to track specific objects. To overcome this problem, a nature‐inspired meta‐heuristic optimization algorithm called Seed Picking Crossover Optimization (SPCO) is proposed to optimize i.e. train the CRF (Conditional Random Field) for choosing relevant feature to segment the object with high accuracy. To meritoriously recognize the objects, a semi‐segmentation process is initially performed using Simple Linear Iterative Clustering (SLIC) algorithm. For pixel transformation and pixel association, Dirichlet process mixture model and CRF are employed. Optimized CRFs are used where the parametric optimization is done using the proposed SPCO algorithm. The proposed work results with 84% on classification accuracy and the performance evaluations are done using MSRC‐21 dataset.
- Published
- 2020
25. Natural variation in meiotic recombination rate shapes introgression patterns in intraspecific hybrids between wild and domesticated barley
- Author
-
Thomas Schmutzer, Klaus Pillen, Steven Dreissig, Andreas Maurer, Rajiv Sharma, Linda Milne, and Andrew J. Flavell
- Subjects
Recombination, Genetic ,0106 biological sciences ,0301 basic medicine ,Candidate gene ,education.field_of_study ,Genome ,Genetic Linkage ,Physiology ,Population ,Crossover ,Introgression ,Hordeum ,Plant Science ,Biology ,01 natural sciences ,Meiosis ,03 medical and health sciences ,030104 developmental biology ,Evolutionary biology ,Allele ,education ,Homologous recombination ,Recombination ,010606 plant biology & botany ,Hybrid - Abstract
Meiotic recombination rates vary considerably between species, populations and individuals. The genetic exchange between homologous chromosomes plays a major role in evolution by breaking linkage between advantageous and deleterious alleles in the case of introgressions. Identifying recombination rate modifiers is thus of both fundamental and practical interest to understand and utilize variation in meiotic recombination rates. We investigated recombination rate variation in a large intraspecific hybrid population (named HEB-25) derived from a cross between domesticated barley and 25 wild barley accessions. We observed quantitative variation in total crossover number with a maximum of a 1.4-fold difference between subpopulations and increased recombination rates across pericentromeric regions. The meiosis-specific α-kleisin cohesin subunit REC8 was identified as a candidate gene influencing crossover number and patterning. Furthermore, we quantified wild barley introgression patterns and revealed how local and genome-wide recombination rate variation shapes patterns of introgression. The identification of allelic variation in REC8 in combination with the observed changes in crossover patterning suggest a difference in how chromatin loops are tethered to the chromosome axis, resulting in reduced crossover suppression across pericentromeric regions. Local and genome-wide recombination rate variation is shaping patterns of introgressions and thereby directly influences the consequences of linkage drag.
- Published
- 2020
26. Virtual Reality as Distraction Analgesia for Office‐Based Procedures: A Randomized Crossover‐Controlled Trial
- Author
-
David Y. Goldrich, Sean McKee, Mingyang L. Gray, Satish Govindaraj, Madeleine R. Schaberg, Anthony Del Signore, and Alfred M. Iloreta
- Subjects
Adult ,Male ,medicine.medical_specialty ,Adolescent ,Crossover ,Anxiety ,Nose ,Virtual reality ,law.invention ,Young Adult ,03 medical and health sciences ,0302 clinical medicine ,Randomized controlled trial ,law ,Distraction ,medicine ,Humans ,In patient ,030212 general & internal medicine ,Aged ,Anxiety reduction ,Office based ,Cross-Over Studies ,business.industry ,Virtual Reality Exposure Therapy ,Endoscopy ,030208 emergency & critical care medicine ,Middle Aged ,Otorhinolaryngologic Surgical Procedures ,Endoscopic sinus surgery ,Ambulatory Surgical Procedures ,Debridement ,Otorhinolaryngology ,Patient Satisfaction ,Physical therapy ,Female ,Surgery ,Analgesia ,business - Abstract
The purpose of this study was to explore the use of immersive and interactive virtual reality (VR) for analgesia, anxiety reduction, and overall satisfaction in patients undergoing outpatient postoperative debridements.Randomized crossover-controlled trial.Academic outpatient clinic.Adult patients who had functional endoscopic sinus surgery and skull base surgery and were undergoing office-based postoperative nasal endoscopy and debridement were recruited and followed for 2 consecutive office visits. Participants were randomized to receive either the control or experimental analgesia for the first postoperative visit (PO1) and crossed over into the opposite treatment arm during the second postoperative visit (PO2). Outcomes included procedural pain, anxiety and satisfaction scores, procedural time, and reflexive head movements per minute (RHM).Eighty-two participants were recruited. At PO1, 39 received standard analgesia, and 43 received an immersive VR experience. At PO1, the VR group experienced significantly less anxiety (VR technology holds promise as a nonpharmacologic analgesic and anxiolytic intervention for otolaryngology office-based procedures. Further study of VR use in other procedures is warranted.1, randomized controlled trial.
- Published
- 2020
27. CCGPA‐MPPT: Cauchy preferential crossover‐based global pollination algorithm for MPPT in photovoltaic system
- Author
-
Priyanka Dixit, Vinu Sundararaj, V. Anoop, Pankaj Bhambri, Rejeesh M R, Regu Sundararaj, Uday Chourasia, and Arundhati Arjaria
- Subjects
Renewable Energy, Sustainability and the Environment ,Computer science ,Control theory ,Photovoltaic system ,Crossover ,Cauchy distribution ,Electrical and Electronic Engineering ,Condensed Matter Physics ,Maximum power point tracking ,Electronic, Optical and Magnetic Materials - Published
- 2020
28. Gene selection and classification using correlation feature selection based binary bat algorithm with greedy crossover
- Author
-
Allin Christe Sundersingh and Akila Seetharaman
- Subjects
Computer Networks and Communications ,Computer science ,business.industry ,Crossover ,Pattern recognition ,Feature selection ,Computer Science Applications ,Theoretical Computer Science ,Correlation ,Gene selection ,Computational Theory and Mathematics ,Binary bat algorithm ,Artificial intelligence ,business ,Software - Published
- 2021
29. Semiparametric copula‐based analysis for treatment effects in the presence of treatment switching
- Author
-
Mey Wang, Chia-Hui Huang, Jinn Li Wang, and Yi-Hau Chen
- Subjects
Statistics and Probability ,Models, Statistical ,Treatment Switching ,Epidemiology ,Computer science ,Proportional hazards model ,Crossover ,Marginal model ,01 natural sciences ,Copula (probability theory) ,Treatment and control groups ,010104 statistics & probability ,03 medical and health sciences ,0302 clinical medicine ,Joint probability distribution ,Covariate ,Econometrics ,Humans ,Computer Simulation ,030212 general & internal medicine ,0101 mathematics ,Marginal distribution ,Probability ,Proportional Hazards Models - Abstract
In controlled trials, "treatment switching" occurs when patients in one treatment group switch to alternative treatments during the trial, and poses challenges to treatment effect evaluation owing to crossover of the treatments groups. In this work, we assume that treatment switching can occur after some disease progression event and view the progression and death events as two semicompeting risks. The proposed model consists of a copula model for the joint distribution of time-to-progression (TTP) and overall survival (OS) up to the earlier of the two events, as well as a conditional hazard model for OS subsequent to progression. The copula model facilitates assessing the marginal distributions of TTP and OS separately from the association between the two events, and, in particular, the treatment effect on OS in the absence of treatment switching. The proposed conditional hazard model for death subsequent to progression allows us to assess the treatment switching (crossover) effect on OS given occurrence of progression and covariates. Semiparametric proportional hazards models are employed in the marginal models for TTP and OS. A nonparametric maximum likelihood procedure is developed for model inference, which is verified through asymptotic theory and simulation studies. The proposed analysis is applied to a lung cancer dataset to illustrate its real utility.
- Published
- 2020
30. Adaptive Position–Based Crossover in the Genetic Algorithm for Data Clustering
- Author
-
Prasenjit Dey and Arnab Gain
- Subjects
Computer science ,Position (vector) ,business.industry ,Crossover ,Genetic algorithm ,k-means clustering ,Pattern recognition ,Artificial intelligence ,Cluster analysis ,business - Published
- 2020
31. Bromomethyl Silicate: A Robust Methylene Transfer Reagent for Radical-Polar Crossover Cyclopropanation of Alkenes
- Author
-
Xiaoping Jin, Yan Li, Jiakan Bao, Yewen Fang, Wenping Luo, Zhang Zongyong, Wu Xiaodong, Yongjun Liu, Tianhang Xu, and Li Zhang
- Subjects
chemistry.chemical_compound ,Chemistry ,Cyclopropanation ,Reagent ,Organic Chemistry ,Polymer chemistry ,Crossover ,Polar ,Physical and Theoretical Chemistry ,Methylene ,Silicate - Published
- 2020
32. How Exhausting!? Emotion Crossover in Organizational Social Networks
- Author
-
Kristin L. Scott, Thomas J. Zagenczyk, and E. Erin Powell
- Subjects
Management of Technology and Innovation ,Strategy and Management ,Crossover ,Business and International Management ,Psychology ,Emotional exhaustion ,Social psychology - Published
- 2020
33. Making Sense of Overlap and Crossover Syndromes
- Author
-
Olivier Chazouillères
- Subjects
medicine.medical_specialty ,business.industry ,Internal medicine ,Sense (molecular biology) ,Crossover ,medicine ,Autoimmune hepatitis ,medicine.disease ,business ,Gastroenterology ,Ursodeoxycholic acid ,medicine.drug ,Primary sclerosing cholangitis - Published
- 2020
34. The evolutionary advantage of fitness‐dependent recombination in diploids: A deterministic mutation–selection balance model
- Author
-
Sviatoslav Rybnikov, Abraham B. Korol, and Zeev Frenkel
- Subjects
0106 biological sciences ,Crossover ,Population genetics ,recombination modifier ,Interference (genetic) ,010603 evolutionary biology ,01 natural sciences ,03 medical and health sciences ,Negative selection ,lcsh:QH540-549.5 ,Ecology, Evolution, Behavior and Systematics ,Selection (genetic algorithm) ,Original Research ,030304 developmental biology ,Nature and Landscape Conservation ,Mathematics ,0303 health sciences ,Ecology ,diploids ,fitness dependence ,recombination ,Evolutionary biology ,Epistasis ,Mutation–selection balance ,lcsh:Ecology ,purifying selection ,Recombination - Abstract
Recombination's omnipresence in nature is one of the most intriguing problems in evolutionary biology. The question of why recombination exhibits certain general features is no less interesting than that of why it exists at all. One such feature is recombination's fitness dependence (FD). The so far developed population genetics models have focused on the evolution of FD recombination mainly in haploids, although the empirical evidence for this phenomenon comes mostly from diploids. Using numerical analysis of modifier models for infinite panmictic populations, we show here that FD recombination can be evolutionarily advantageous in diploids subjected to purifying selection. We ascribe this advantage to the differential rate of disruption of lower‐ versus higher‐fitness genotypes, which can be manifested in selected systems with at least three loci. We also show that if the modifier is linked to such selected system, it can additionally benefit from modifying this linkage in a fitness‐dependent manner. The revealed evolutionary advantage of FD recombination appeared robust to crossover interference within the selected system, either positive or negative. Remarkably, FD recombination was often favored in situations where any constant nonzero recombination was evolutionarily disfavored, implying a relaxation of the rather strict constraints on major parameters (e.g., selection intensity and epistasis) required for the evolutionary advantage of nonzero recombination formulated by classical models., An amazing feature of recombination is fitness dependence (FD). The so far developed models have focused on the evolution of FD recombination mainly in haploids, although the empirical evidence for this phenomenon comes mostly from diploids. Using numerical analysis of modifier models for infinite panmictic populations, we show here that FD recombination can be evolutionarily advantageous in diploids subjected to purifying selection. We ascribe this advantage to the differential rate of disruption of lower‐ versus higher‐fitness genotypes, which can be manifested in selected systems with at least three loci.
- Published
- 2020
35. Biosimilars of low molecular weight heparins
- Subjects
formulary ,low molecular weight heparin ,anticoagulant ,BRANDED ENOXAPARIN ,SOCIETY ,HEALTHY-SUBJECTS ,UNITED-STATES ,CROSSOVER ,OPEN-LABEL ,PRODUCT ,THROMBOSIS ,CONTAMINANTS ,biosimilar ,generics ,BIOEQUIVALENCE - Abstract
Biosimilars of low molecular weight heparins (LMWHs) are more alike the originator than different branded LMWHs. The latter differ largely in molecular weight, anti-FXa/anti-FIIa ratio and antithrombin binding. The Food and Drug Administration and European Medicines Agency guidelines are sufficient for the clinical use of high quality LMWHs. However, the Food and Drug Administration guideline lacks the results of a phase I clinical trial in the approval process. Most information about biosimilars is available for enoxaparin given that many biosimilars of enoxaparin have received market access. The guidelines of many International Thrombosis Societies for LMWH biosimilars are too stringent, not updated and impractical for formulary uptake discussions. This review gives background information on critical factors for the formulary uptake process of LMWHs with special attention for the use of the System of Objectified Judgment Analysis/Infomatrix model.
- Published
- 2019
36. DeepTetrad: high‐throughput image analysis of meiotic tetrads by deep learning inArabidopsis thaliana
- Author
-
Eun Jung Kim, Gregory P. Copenhaver, Ian R. Henderson, Dohwan Byun, Jaeil Kim, Ji Hye Park, Il Doo Hwang, Yeongmi Park, Euncheon Lim, Juhyun Kim, Kyuha Choi, and Hyun Seob Cho
- Subjects
0106 biological sciences ,0301 basic medicine ,Crossover ,Arabidopsis ,Plant Science ,Interference (genetic) ,01 natural sciences ,Chromosomes, Plant ,Chromosome segregation ,03 medical and health sciences ,Deep Learning ,Meiosis ,Chromosome Segregation ,Genetics ,Crossing Over, Genetic ,Transgenes ,Homologous Recombination ,Tetrad ,Alleles ,biology ,Arabidopsis Proteins ,fungi ,Inheritance (genetic algorithm) ,food and beverages ,Cell Biology ,biology.organism_classification ,030104 developmental biology ,Evolutionary biology ,Pollen ,Homologous recombination ,010606 plant biology & botany - Abstract
Meiotic crossovers facilitate chromosome segregation and create new combinations of alleles in gametes. Crossover frequency varies along chromosomes and crossover interference limits the coincidence of closely spaced crossovers. Crossovers can be measured by observing the inheritance of linked transgenes expressing different colors of fluorescent protein in Arabidopsis pollen tetrads. Here we establish DeepTetrad, a deep learning-based image recognition package for pollen tetrad analysis that enables high-throughput measurements of crossover frequency and interference in individual plants. DeepTetrad will accelerate the genetic dissection of mechanisms that control meiotic recombination.
- Published
- 2019
37. Short Versus Conventional Pulse‐Width Deep Brain Stimulation in Parkinson's Disease: A Randomized Crossover Comparison
- Author
-
Harith Akram, Elina Tripoliti, Viswas Dayal, Timothy Grover, Catherine Milabo, Maricel Salazar, Marwan Hariz, Patricia Limousin, Thomas Foltynie, Joseph Candelario-McKeown, Dilan Athauda, and Ludvic Zrinzo
- Subjects
Male ,0301 basic medicine ,medicine.medical_specialty ,Deep brain stimulation ,Neurology ,Parkinson's disease ,Deep Brain Stimulation ,medicine.medical_treatment ,Crossover ,03 medical and health sciences ,Dysarthria ,0302 clinical medicine ,Double-Blind Method ,Subthalamic Nucleus ,Internal medicine ,medicine ,Humans ,Aged ,Cross-Over Studies ,business.industry ,Subthalamic nucleus deep brain stimulation ,food and beverages ,Parkinson Disease ,Middle Aged ,medicine.disease ,nervous system diseases ,Treatment Outcome ,surgical procedures, operative ,030104 developmental biology ,nervous system ,Quality of Life ,Cardiology ,Female ,Neurology (clinical) ,medicine.symptom ,business ,therapeutics ,030217 neurology & neurosurgery - Abstract
Subthalamic nucleus deep brain stimulation (STN-DBS) is an effective therapy for selected Parkinson's disease patients with motor fluctuations, but can adversely affect speech and axial symptoms. The use of short pulse width (PW) has been shown to expand the therapeutic window acutely, but its utility in reducing side effects in chronic STN-DBS patients has not been evaluated.To compare the effect of short PW settings using 30-μs with conventional 60-μs settings on stimulation-induced dysarthria in Parkinson's disease patients with previously implanted STN-DBS systems.In this single-center, double-blind, randomized crossover trial, we assigned 16 Parkinson's disease patients who had been on STN-DBS for a mean of 6.5 years and exhibited moderate dysarthria to 30-μs or 60-μs settings for 4 weeks followed by the alternative PW setting for a further 4 weeks. The primary outcome was difference in dysarthric speech measured by the Sentence Intelligibility Test between study baseline and the 2 PW conditions. Secondary outcomes included motor, nonmotor, and quality of life measures.There was no difference in the Sentence Intelligibility Test scores between baseline and the 2 treatment conditions (P = 0.25). There were also no differences noted in motor, nonmotor, or quality of life scores. The 30-μs settings were well tolerated, and adverse event rates were similar to those at conventional PW settings. Post hoc analysis indicated that patients with dysarthria and a shorter duration of DBS may be improved by short PW stimulation.Short PW settings using 30 μs did not alter dysarthric speech in chronic STN-DBS patients. A future study should evaluate whether patients with shorter duration of DBS may be helped by short PW settings. © 2019 International Parkinson and Movement Disorder Society.
- Published
- 2019
38. Photoredox‐Catalyzed Cyclopropanation of 1,1‐Disubstituted Alkenes via Radical‐Polar Crossover Process
- Author
-
Yewen Fang, Yan Li, Guicai Zhao, Wanli Zhou, Li Zhang, Tingting Xia, Xinxin Zhang, Xiaoping Jin, Bin Chen, Wenping Luo, and Yi Yang
- Subjects
Chemistry ,Cyclopropanation ,Scientific method ,Organic Chemistry ,Crossover ,Photocatalysis ,Photoredox catalysis ,Polar ,Photochemistry ,Catalysis - Published
- 2019
39. Ultra‐wideband crossover with a reversed polarity channel designed with normalized Euclid distance for fast pulse transmission
- Author
-
Leilei Liu, Qiuyi Zhang, Shunli Li, Hongxin Zhao, Mei Yang, and Xiaoxing Yin
- Subjects
Physics ,Fast pulse ,business.industry ,Crossover ,Ultra-wideband ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Optics ,Transmission (telecommunications) ,Reversed polarity ,Electrical and Electronic Engineering ,business ,Communication channel - Published
- 2019
40. A hybrid artificial bee colony algorithm for scheduling of digital microfluidic biochip operations
- Author
-
K. Rajesh and Sumanta Pyne
- Subjects
Computer Networks and Communications ,Computer science ,business.industry ,Crossover ,Microfluidics ,Scheduling (production processes) ,Lab-on-a-chip ,Computer Science Applications ,Theoretical Computer Science ,law.invention ,Artificial bee colony algorithm ,Computational Theory and Mathematics ,law ,Embedded system ,Digital microfluidics ,business ,Biochip ,Software - Published
- 2021
41. Review for 'Reducing the Need for Carbohydrate Counting in Type 1 Diabetes using Closed-Loop Automated Insulin Delivery (Artificial Pancreas) and Empagliflozin: A Randomised Controlled Non-Inferiority Crossover Pilot Trial'
- Author
-
Johan Jendle
- Subjects
medicine.medical_specialty ,Type 1 diabetes ,business.industry ,Crossover ,Urology ,Insulin delivery ,medicine.disease ,Artificial pancreas ,Carbohydrate counting ,Non inferiority ,Empagliflozin ,medicine ,business ,Closed loop - Published
- 2021
42. Analysis of fractional COVID-19 epidemic model under Caputo operator
- Author
-
Rahat Zarin, Amir Khan, Abdullahi Yusuf, Sayed Abdel‐Khalek, Mustafa Inc, and Mühendislik ve Doğa Bilimleri Fakültesi
- Subjects
Lyapunov function ,Special Issue Papers ,Coronavirus disease 2019 (COVID-19) ,General Mathematics ,Crossover ,General Engineering ,Regular polygon ,Fixed-point theorem ,Stability (probability) ,Numerical Simulations ,34d45 ,symbols.namesake ,Operator (computer programming) ,Sensitivity Analysis ,Stability Analysis ,Special Issue Paper ,Epidemic Model ,symbols ,Applied mathematics ,Uniqueness ,Sensitivity (control systems) ,26a33 ,Epidemic model ,Mathematics - Abstract
The article deals with the analysis of the fractional COVID‐19 epidemic model (FCEM) with a convex incidence rate. Keeping in view the fading memory and crossover behavior found in many biological phenomena, we study the coronavirus disease by using the noninteger Caputo derivative (CD). Under the Caputo operator (CO), existence and uniqueness for the solutions of the FCEM have been analyzed using fixed point theorems. We study all the basic properties and results including local and global stability. We show the global stability of disease‐free equilibrium using the method of Castillo‐Chavez, while for disease endemic, we use the method of geometrical approach. Sensitivity analysis is carried out to highlight the most sensitive parameters corresponding to basic reproduction number. Simulations are performed via first‐order convergent numerical technique to determine how changes in parameters affect the dynamical behavior of the system.
- Published
- 2021
43. Stress Spillover and Crossover in Couple Relationships: Integrating Religious Beliefs and Prayer
- Author
-
Ross W. May, Frank D. Fincham, and Ashley N. Cooper
- Subjects
Health (social science) ,Couple stress ,Social Psychology ,Spillover effect ,media_common.quotation_subject ,Stress (linguistics) ,Crossover ,Psychology ,Social psychology ,Social Sciences (miscellaneous) ,Prayer ,media_common - Published
- 2019
44. Spillover and crossover of work resources: A test of the positive flow of resources through work–family enrichment
- Author
-
Wayne S. Crawford, Dawn S. Carlson, Merideth J. Thompson, and K. Michele Kacmar
- Subjects
Work–family enrichment ,Organizational Behavior and Human Resource Management ,Sociology and Political Science ,Crossover ,Environmental economics ,Quality of work life ,Test (assessment) ,Flow (mathematics) ,Work (electrical) ,Spillover effect ,Psychology ,General Psychology ,Applied Psychology ,Work scheduling - Published
- 2019
45. Preparation of Alkyl Boronic Esters Using Radical‐Polar Crossover Reactions of Vinylboron Ate Complexes
- Author
-
Helene Wolleb, Armido Studer, Erick M. Carreira, and Marvin Kischkewitz
- Subjects
chemistry.chemical_classification ,chemistry ,010405 organic chemistry ,Crossover ,Polymer chemistry ,Polar ,010402 general chemistry ,01 natural sciences ,Alkyl ,0104 chemical sciences - Published
- 2019
46. Accounting for a decaying correlation structure in cluster randomized trials with continuous recruitment
- Author
-
Andrew Forbes, Karla Hemming, Stephane Heritier, Kelsey L. Grantham, and Jessica Kasza
- Subjects
Statistics and Probability ,Time Factors ,Epidemiology ,Crossover ,Context (language use) ,01 natural sciences ,Correlation ,010104 statistics & probability ,03 medical and health sciences ,0302 clinical medicine ,Outcome Assessment, Health Care ,Statistics ,Diabetes Mellitus ,Range (statistics) ,Cluster Analysis ,Humans ,030212 general & internal medicine ,Cluster randomised controlled trial ,0101 mathematics ,Randomized Controlled Trials as Topic ,Mathematics ,Cross-Over Studies ,Models, Statistical ,Patient Selection ,Estimator ,Variance (accounting) ,Sample size determination ,Sample Size - Abstract
A requirement for calculating sample sizes for cluster randomized trials (CRTs) conducted over multiple periods of time is the specification of a form for the correlation between outcomes of subjects within the same cluster, encoded via the within-cluster correlation structure. Previously proposed within-cluster correlation structures have made strong assumptions; for example, the usual assumption is that correlations between the outcomes of all pairs of subjects are identical ("uniform correlation"). More recently, structures that allow for a decay in correlation between pairs of outcomes measured in different periods have been suggested. However, these structures are overly simple in settings with continuous recruitment and measurement. We propose a more realistic "continuous-time correlation decay" structure whereby correlations between subjects' outcomes decay as the time between these subjects' measurement times increases. We investigate the use of this structure on trial planning in the context of a primary care diabetes trial, where there is evidence of decaying correlation between pairs of patients' outcomes over time. In particular, for a range of different trial designs, we derive the variance of the treatment effect estimator under continuous-time correlation decay and compare this to the variance obtained under uniform correlation. For stepped wedge and cluster randomized crossover designs, incorrectly assuming uniform correlation will underestimate the required sample size under most trial configurations likely to occur in practice. Planning of CRTs requires consideration of the most appropriate within-cluster correlation structure to obtain a suitable sample size.
- Published
- 2019
47. Enhanced sampling method in molecular simulations using genetic algorithm for biomolecular systems
- Author
-
John E. Straub, Yoshitake Sakae, and Yuko Okamoto
- Subjects
Quantitative Biology::Biomolecules ,010304 chemical physics ,Protein Conformation ,Computer science ,Sampling efficiency ,Monte Carlo method ,Crossover ,Molecular simulation ,General Chemistry ,Molecular Dynamics Simulation ,Dihedral angle ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Computational Mathematics ,Molecular dynamics ,Distribution (mathematics) ,0103 physical sciences ,Genetic algorithm ,Peptides ,Algorithm ,Algorithms - Abstract
We propose a molecular simulation method using genetic algorithm (GA) for biomolecular systems to obtain ensemble averages efficiently. In this method, we incorporate the genetic crossover, which is one of the operations of GA, to any simulation method such as conventional molecular dynamics (MD), Monte Carlo, and other simulation methods. The genetic crossover proposes candidate conformations by exchanging parts of conformations of a target molecule between a pair of conformations during the simulation. If the candidate conformations are accepted, the simulation resumes from the accepted ones. While conventional simulations are based on local update of conformations, the genetic crossover introduces global update of conformations. As an example of the present approach, we incorporated genetic crossover to MD simulations. We tested the validity of the method by calculating ensemble averages and the sampling efficiency by using two kinds of peptides, ALA3 and (AAQAA)3 . The results show that for ALA3 system, the distribution probabilities of backbone dihedral angles are in good agreement with those of the conventional MD and replica-exchange MD simulations. In the case of (AAQAA)3 system, our method showed lower structural correlation of α-helix structures than the other two methods and more flexibility in the backbone ψ angles than the conventional MD simulation. These results suggest that our method gives more efficient conformational sampling than conventional simulation methods based on local update of conformations. © 2018 Wiley Periodicals, Inc.
- Published
- 2018
48. Power and sample size requirements for GEE analyses of cluster randomized crossover trials
- Author
-
Elizabeth L. Turner, John S. Preisser, Andrew Forbes, and Fan Li
- Subjects
Statistics and Probability ,Epidemiology ,Covariance matrix ,Crossover ,Estimator ,Estimating equations ,01 natural sciences ,Crossover study ,010104 statistics & probability ,03 medical and health sciences ,0302 clinical medicine ,Sample size determination ,Statistics ,030212 general & internal medicine ,0101 mathematics ,Generalized estimating equation ,Eigenvalues and eigenvectors ,Mathematics - Abstract
The cluster randomized crossover design has been proposed to improve efficiency over the traditional parallel cluster randomized design, which often involves a limited number of clusters. In recent years, the cluster randomized crossover design has been increasingly used to evaluate the effectiveness of health care policy or programs, and the interest often lies in quantifying the population-averaged intervention effect. In this paper, we consider the two-treatment two-period crossover design, and develop sample size procedures for continuous and binary outcomes corresponding to a population-averaged model estimated by generalized estimating equations, accounting for both within-period and interperiod correlations. In particular, we show that the required sample size depends on the correlation parameters through an eigenvalue of the within-cluster correlation matrix for continuous outcomes and through two distinct eigenvalues of the correlation matrix for binary outcomes. We demonstrate that the empirical power corresponds well with the predicted power by the proposed formulae for as few as eight clusters, when outcomes are analyzed using the matrix-adjusted estimating equations for the correlation parameters concurrently with a suitable bias-corrected sandwich variance estimator.
- Published
- 2018
49. Design and monitoring of survival trials in complex scenarios
- Author
-
Hui Quan, Xiaodong Luo, Steven Bai, Junshan Qiu, Xuezhou Mao, and Xun Chen
- Subjects
Statistics and Probability ,Mathematical optimization ,Time Factors ,Epidemiology ,Computer science ,Crossover ,01 natural sciences ,010104 statistics & probability ,03 medical and health sciences ,0302 clinical medicine ,Piecewise exponential ,Humans ,030212 general & internal medicine ,0101 mathematics ,Statistic ,Proportional Hazards Models ,Event (probability theory) ,Clinical Trials as Topic ,Cross-Over Studies ,Models, Statistical ,Delayed treatment ,Survival Analysis ,Markov Chains ,Exponential function ,Range (mathematics) ,Treatment Outcome - Abstract
This paper proposes an approach to design and monitor survival trials accounting for complex scenarios such as delayed treatment effect, treatment dilution, and treatment crossover. These scenarios often lead to non-proportional hazards, making study design and monitoring more difficult. We demonstrate that, with event times following piecewise exponential distributions, the log-rank statistic as well as its variance-covariance structure can be easily computed, which greatly simplifies study design and monitoring. As the number of pieces in the exponential distributions can be arbitrary, this approach can handle a wide range of scenarios. Three hypothetical examples are used to demonstrate its potential use.
- Published
- 2018
50. Blinded and unblinded sample size reestimation in crossover trials balanced for period
- Author
-
Adrian Mander, Michael J. Grayling, and James Wason
- Subjects
Statistics and Probability ,Biometry ,Randomization ,Blinding ,Computer science ,Crossover ,Kaplan-Meier Estimate ,01 natural sciences ,Statistics, Nonparametric ,sample size reestimation ,010104 statistics & probability ,03 medical and health sciences ,0302 clinical medicine ,Statistics ,Humans ,030212 general & internal medicine ,0101 mathematics ,Clinical Trials as Topic ,Cross-Over Studies ,Models, Statistical ,Clinical study design ,Estimator ,Issues in Complex Clinical Trials ,General Medicine ,Crossover study ,blinded ,Sample size determination ,Sample Size ,Adaptive design ,Heart Transplantation ,Regression Analysis ,crossover trial ,Statistics, Probability and Uncertainty ,internal pilot study ,Research Paper - Abstract
The determination of the sample size required by a crossover trial typically depends on the specification of one or more variance components. Uncertainty about the value of these parameters at the design stage means that there is often a risk a trial may be under‐ or overpowered. For many study designs, this problem has been addressed by considering adaptive design methodology that allows for the re‐estimation of the required sample size during a trial. Here, we propose and compare several approaches for this in multitreatment crossover trials. Specifically, regulators favor reestimation procedures to maintain the blinding of the treatment allocations. We therefore develop blinded estimators for the within and between person variances, following simple or block randomization. We demonstrate that, provided an equal number of patients are allocated to sequences that are balanced for period, the proposed estimators following block randomization are unbiased. We further provide a formula for the bias of the estimators following simple randomization. The performance of these procedures, along with that of an unblinded approach, is then examined utilizing three motivating examples, including one based on a recently completed four‐treatment four‐period crossover trial. Simulation results show that the performance of the proposed blinded procedures is in many cases similar to that of the unblinded approach, and thus they are an attractive alternative.
- Published
- 2018
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.