Enhanced piezoelectricity of PVDF nanofibers via a plasticizer treatment for energy harvesting

Enhancing the electrical outputs of energy harvesters is a great demand for researchers in recent years. In this work, the effect of the plasticizer treatment (Tetrahydrofuran [THF]) on the β phase content (F[β]) of electrospun polyvinylidene fluoride (PVDF) fiber webs which are used as active layers to directly make a piezoelectric nanogenerator (PENG) is demonstrated. The results showed that during the plasticizer treatment, the F(β) of the web increases when the initial length of the web (L0) equals the distance between the two ends of the solid support (L) which the web fixed on it, whereas the F(β) decreases when L < L0 resulting in the formation of crimped fibers. Furthermore, the electrical outputs of the PENG based on the pristine web, and treated webs at different lengths are investigated. We believe this work can be used as a good reference for enhancing the electrical outputs of the PENG by enhancing the F (β) of PVDF nanofiber webs using a plasticizer treatment.

Ensemble slice sampling

Slice sampling has emerged as a powerful Markov Chain Monte Carlo algorithm that adapts to the characteristics of the target distribution with minimal hand-tuning. However, Slice Sampling’s performance is highly sensitive to the user-specified initial length scale hyperparameter and the method generally struggles with poorly scaled or strongly correlated distributions. This paper introduces Ensemble Slice Sampling (ESS), a new class of algorithms that bypasses such difficulties by adaptively tuning the initial length scale and utilising an ensemble of parallel walkers in order to efficiently handle strong correlations between parameters. These affine-invariant algorithms are trivial to construct, require no hand-tuning, and can easily be implemented in parallel computing environments. Empirical tests show that Ensemble Slice Sampling can improve efficiency by more than an order of magnitude compared to conventional MCMC methods on a broad range of highly correlated target distributions. In cases of strongly multimodal target distributions, Ensemble Slice Sampling can sample efficiently even in high dimensions. We argue that the parallel, black-box and gradient-free nature of the method renders it ideal for use in scientific fields such as physics, astrophysics and cosmology which are dominated by a wide variety of computationally expensive and non-differentiable models.

The Six Ages of the World and Biblical Genealogy in Anglo-Saxon Encyclopaedic Notes

In the early medieval period, history was commonly organised into six epochs lasting roughly one thousand years each, according to certain calculations of the world’s age. The idea of the six ages emerged from and was consolidated by allegorical interpretations of the Hexameron in which the material endurance of the world was thought to mirror the initial length of its Creation. This historical schematisation enjoyed widespread currency in Anglo-Saxon England, even after Bede had proved that the world was not, in fact, approaching 6,000 years. This article analyses how the topos of the six ages is used and adapted within a hitherto understudied group of related encyclopaedic notes in three Anglo-Saxon manuscripts. How these texts relate to and differ from the wider corpus of encyclopaedic texts on this subject is also charted. The following study investigates the ways in which encyclopaedic texts on the six ages were adapted, expanded and transmitted, and the religious and political motivations driving such changes. This article offers the first in-depth analysis of this particular group of texts, foregrounding the sophistication of micro-texts that explain the six ages. Overall, this study emphasises the pedagogical, theological and historiographical applications of this concept in early medieval English thought.

High-Frequency Repeated Measures of Over 5,000 Infants Aged 6–27 Months Reveals Pattern of Growth Faltering in Rural Burkina Faso

Objectives Linear growth faltering, failure to achieve one's potential for length or height at each age, is associated with increased risk of mortality and morbidity. Understanding the age-related patterns of growth faltering can inform timing of interventions and policies for prevention; however current knowledge is limited by cross-sectional data. We examine the longitudinal characterization of the timing of growth faltering among young children. Methods Using longitudinal anthropometric data originally collected as part of a food-aid cost-effectiveness trial, we investigated individual growth curves of 5,039 children aged 6–27 months in Burkina Faso (108,580 total measurements) to determine whether growth faltering occurs through intermittent episodes of slower growth, or continuously slow growth. We visualized individual growth curves and used two-stage regressions to evaluate growth curve smoothness at different levels of attained length. To do this, we first obtained model fit and diagnostic parameters from individual regressions of each child's length on their age. Parameters extracted included R2, as a metric of curve smoothness, initial length at 6 months, and average velocity. We then regressed these parameters on individual-level attained length at study end. Results Growth faltering manifests as both continuously lower growth velocity throughout the observation period and greater heterogeneity in growth velocity amplitude. Children with lower attained length start smaller (Quintile 1 of attained length-63.1 cm initial length; Quintile 5-68.4 cm) and stay on their initial trajectories, continuously growing slower than their taller counterparts. In addition, a 0.01 increase in the R2 (smoothness) from regression of a child's length on their age is associated with a 3.10 cm increase in attained length (95% CI: 2.80, 3.41), showing that smoother growth is also associated with higher attained length. Conclusions Children who experience the most extreme growth faltering are likely to be less resilient to systematic growth-limiting conditions as well as episodic insults to their growth. Future research should investigate ways of improving environmental conditions to support growth. Funding Sources Financial support provided by the Food Aid Quality Review project, funded by the United States Agency for International Development.

Cavatappi artificial muscles from drawing, twisting, and coiling polymer tubes

Compliant, biomimetic actuation technologies that are both efficient and powerful are necessary for robotic systems that may one day interact, augment, and potentially integrate with humans. To this end, we introduce a fluid-driven muscle-like actuator fabricated from inexpensive polymer tubes. The actuation results from a specific processing of the tubes. First, the tubes are drawn, which enhances the anisotropy in their microstructure. Then, the tubes are twisted, and these twisted tubes can be used as a torsional actuator. Last, the twisted tubes are helically coiled into linear actuators. We call these linear actuators cavatappi artificial muscles based on their resemblance to the Italian pasta. After drawing and twisting, hydraulic or pneumatic pressure applied inside the tube results in localized untwisting of the helical microstructure. This untwisting manifests as a contraction of the helical pitch for the coiled configuration. Given the hydraulic or pneumatic activation source, these devices have the potential to substantially outperform similar thermally activated actuation technologies regarding actuation bandwidth, efficiency, modeling and controllability, and practical implementation. In this work, we show that cavatappi contracts more than 50% of its initial length and exhibits mechanical contractile efficiencies near 45%. We also demonstrate that cavatappi artificial muscles can exhibit a maximum specific work and power of 0.38 kilojoules per kilogram and 1.42 kilowatts per kilogram, respectively. Continued development of this technology will likely lead to even higher performance in the future.

INVESTIGATION OF HOT PLASTIC DEFORMATION OF LABORATORY AXIAL FLOATS

A review of research in the field of modeling experiments on heat treatment and pressure treatment of metal and the impact on the physical and mechanical properties of steel with a chemical composition of 0.59% C, 0.31% Si, 0.73% Mn. A mathematical model for calculating the physical and mechanical properties of steel in the process of hot plastic deformation has been developed and prospects for further development of research in this area have been identified. As a result of modeling, the following functions were obtained: the amount of deformation in the direction of the applied force divided by the initial length of the material. The coefficient of elongation of the material with the actual chemical composition at a temperature of 1250 ± 10 ° C, which was 0.32. When comparing the values of the load that was applied to the GPA in the laboratory and the results of calculations using the developed model, it was found that they have close values of about 45 MPa. This confirms the adequacy of the obtained model.A review of research in the field of modeling experiments on heat treatment and pressure treatment of metal and the impact on the physical and mechanical properties of steel with a chemical composition of 0.59% C, 0.31% Si, 0.73% Mn. A mathematical model for calculating the physical and mechanical properties of steel in the process of hot plastic deformation has been developed and prospects for further development of research in this area have been identified. As a result of modeling, the following functions were obtained: the amount of deformation in the direction of the applied force divided by the initial length of the material. The coefficient of elongation of the material with the actual chemical composition at a temperature of 1250 ± 10 ° C, which was 0.32. When comparing the values of the load that was applied to the GPA in the laboratory and the results of calculations using the developed model, it was found that they have close values of about 45 MPa. This confirms the adequacy of the obtained model.

Role of plantar aponeurosis in the formation of cavus component in recurrent congenital equinocavovarus deformity

Background. Congenital equinocavovarus deformity (CECVD) is the second most frequent among all congenital disorders of the musculoskeletal system in children, and one of the most common causes of childhood disability in Ukraine. The incidence of CECVD reaches 1–3 cases per 1,000 newborns (35–40 % of all foot deformities). According to some authors, plantar fasciotomy can improve the shape and function of support and walking in these patients. The purpose was to determine the role of plantar aponeurosis in the formation of the cavus component in cases of recurrent CECVD in children. Material and methods. Mathematical researches were carried out using the graph-analytical method. Results. To reduce the arch height when correcting pes cavus, it is necessary to increase significantly the length of the aponeurosis (up to 25 % of its initial length). To perform this task, a significant tensile force must be applied to the aponeurosis, the value of which depends on the magnitude of a decrease in the arch height. So, to reduce the arch height by 10 mm, it is necessary to lengthen the aponeurosis by 12 mm, for which a constant force of 932 N must be applied to it. To reduce the arch height by 20 mm, the magnitude of the tensile force applied to the aponeurosis must be increased to 1,438 N, which is almost impossible. Therefore, the presence of a shortened aponeurosis is a significant obstacle for the effective correction of pes cavus. Conclusions. Correction of pes cavus requires a significant decrease in the height of its longitudinal arch, which leads to a significant lengthening of the aponeurosis, up to 25 % of its initial length. To ensure an increase in the length of the aponeurosis, the presence of a significant constant tensile force that exceeds 1000 N is necessary. Plantar aponeurosis plays a direct role in supporting the longitudinal arch of the foot, and is one of the causes for the persistence of pes cavus in patients with recurrent CECVD, which does not respond to conservative treatment. To correct cavus foot, in the failure of conservative treatment, it is necessary to lengthen it by surgical intervention (intersection). The value of the angle of the longitudinal arch of the foot of 110° can be chosen as a criterion for choosing a decision in favor of preserving or resection of the aponeurosis.

INVESTIGATION OF THE EFFECTIVENESS OF CONCURRENT APPLICATION OF CENTRAL NERVOUS SYSTEM ELECTRICAL TRANQUILIZATION AND PEPTIDE BIOREGULATOR CORTEXIN IN IMPROVEMENT OF THE HUMAN STATOKINETIC STABILITY

The paper deals with effectiveness of 2-wk electrical tranquilization of the central nervous system (CNS ET) combined with peptide bioregulator cortexin in improvement of the statokinetic stability. Statokinetic loads were modeled using the standard test of continuous Coriolis accelerations accumulation (CCAT). Cortexin was applied intranasally twice a day at the dose of 5 mg. It was shown that CNS ET together with cortex extends the CCAT tolerance and alleviates sensory, autonomic and somatic components of statokinetic reactions. Tolerance time was the longest immediately after the course; over 3 months tolerance returned gradually to initial length.