Weak Core Research Articles

Nonlinear mechanics of sandwich plates: Layerwise third-order thickness and shear deformation theory

The nonlinear mechanics of sandwich plates is studied using a layerwise third-order thickness and shear deformation theory. In particular, the two face sheets are modelled using a second-order shear deformation theory (well-justified in case of a zero-shear stress only at one outer surface) and the core is modelled with a third-order thickness and transverse shear deformation theory. After introducing continuity of displacements at the interfaces between the core and the face sheets, 16 independent kinematic parameters are retained. An independent parameter is kept to describe the thickness deformation, which allows for introduction of the corresponding boundary condition; this represents a significant novel contribution. Geometric nonlinearity in all the kinematic parameters is introduced. Numerical results are presented for deflection of a sandwich plate under pressure. A thin core was considered, since it is numerically more critical, and a wide range of core stiffnesses was studied in order to verify the validity of the proposed model till the limit case of two plates joined by a core of negligible stiffness (i.e., two independent plates). Numerical results are compared to those obtained by a commercial finite element (FE) program with three-dimensional solid elements till the limit when the FE code fails for large deformations of the extremely weak core.

Dietary affinities, resource overlap and core structure in Atlantic Forest phyllostomid bat communities

Abstract The Phyllostomidae is arguably the most diverse family‐level clade of mammals. Associated with this high diversity is considerable heterogeneity in resource utilisation among species and across locales of the Neotropics. Despite heterogeneity, few attempts have been made to synthesise dietary patterns even for smaller regions within the Neotropics. Atlantic Forest is a large dynamic ecoregion in the southern Neotropics that is distinct from other Tropical forests because of its extensive latitudinal extent, elevated climatic heterogeneity, biodiversity and long history of anthropogenic modification. I obtained data on dietary affinities of 34 species of bats from 35 different sites spanning the entire Atlantic Forest. In Atlantic Forest, as in other places in the Neotropics, phyllostomids consumed arthropods, vertebrates, fruits, nectar and blood. Frugivores consumed and dispersed the fruits of 99 different species of plants and nectarivores pollinated an additional nine others. Dietary overlap was modest, yet significantly greater than expected based on a null model. The main axis of variation in diet separated species that primarily consumed animal material from those that primarily consumed plant material and this axis was significantly related to phylogenetic affinities of species. Unlike in other places in the Neotropics, frugivorous bats did not exhibit a core structure related to genus‐to‐genus matching of bat genera with plant genera. Generality of diets of frugivorous bats, further indicated by non‐randomly high dietary overlap, is likely to degrade core structure in these primarily Subtropical communities. Co‐occurrence of a large number of generalist bat species, seasonal climates and ubiquitous anthropogenic modification may serve to promote generality of resource utilisation of bats in Atlantic Forest. The Neotropics is vast and the bats that live within it are diverse. Future studies should explore spatial dynamics of dietary affinities and resource overlap to increase understanding of the context of strong and weak core structure of phyllostomid bat communities.

Weak core inverses and pseudo core inverses in a ring with involution

In 2020, Ferreyra et al. defined the weak core inverse of a complex matrix. We generalize it to a unitary ring with involution and investigate the relationship between the weak core inverse and the m-weak group inverse. Furthermore, we prove that an element is pseudo core invertible if this element is both {1, 3}-invertible and weak group invertible. Then, we show that each nilpotent element is Moore–Penrose invertible if and only if each pseudo core invertible element is weak core invertible. Finally, we consider the conditions under which the weak core inverse of an element coincides with another generalized inverse.

Queen of the Dryads

Queen of the Dryads Sophia Veltfort (bio) Seth had left for work by the time the stranger entered Sophie's bedroom: a stiffly upright woman with white-gold hair to her waist. She wasn't the landlady or anyone Sophie had seen in the building. Seth had probably left the front door unlocked, again. You'll come home one day and I'll be missing, she'd told him, or dead, our valuables gone. What valuables? he'd wanted to know. "You'd better get up, Sophie," the stranger said, not moving from the doorway. Her words were quick and precise. "You're dancing the Queen of the Dryads at the National Ballet Theater this evening." It was six thirty in the morning, five hours before Sophie's alarm was set to go off. On her forearm the red and green remnants of a temporary tattoo suggested the image of a radish. With effort Sophie recalled someone pressing a wet blue washcloth to her skin the night before, at Seth's birthday party. Since then, sweat had shifted pieces of the leaves from her wrist to her watchband. She thought she might still be drunk. She reached for her cell phone as she examined the woman more carefully. Below a wide-set jaw, the contours of the woman's chest bones fanned out from her sternum like flying buttresses. Last night Seth had complained that Sophie never danced with him, never kissed him, never tried to look pretty anymore. Not true, she'd said, brandishing her forearm: it's a ravishing radish. She'd taken care to wear a dress he liked, an old purple bodycon from college that still looked okay if she held her stomach tight and stood up straight. "Did Seth send you?" Sophie asked. "Is this a weird sex thing?" "It's act two, scene three of Don Quixote," the woman said impatiently. "Get up." "That's a book, not a play. I've read it." In fact she had read only the Prologue. [End Page 85] "It's a ballet," the woman said. "Choreographed for the Imperial Theatre in 1869. Adapted in 1900 and 1902." As a kid Sophie had taken dance classes. Her fellow students had laughed at her weak core and quadriceps, the way her abs strained vainly during floor exercises. But the teacher had drawn the class's attention to the easy arch of her feet, the natural turnout of her hip rotator. Sophie liked to think that couched in her weak, flexible figure lay a wellspring of possible greatness. In the stranger's error, Sophie savored the alternate reality in which she had tapped that potential and become a dancer of singular ability. She imagined that deep down she knew the choreography, that this performance had been scheduled for a long time. "Look," the woman said. "There's a car downstairs. You've wasted any time for breakfast, so bring a power bar." Sophie protested that she had no power bars, but the woman had picked up her cell phone and was murmuring animatedly into its base. Sophie got out of bed and raised the window blinds. Pale light sloped into her bedroom, and she gaped at the beauty she slept through every morning. In the early light she felt vested with new ability, quickness, and composure. She did not feel like a fraudulent human being. "Are you going to gawk out the window all day? I've told you we're late," the woman hissed. "Are you the audience or the Queen of the Dryads?" Sophie searched the room for appropriate clothes. On the floor her purple dress from the night before lay crumpled beside Seth's socks and boxers. She pulled on the blue jeans she wore most days and a scratchy black sweater with a leotard neckline. ________ From the back seat of a maroon Honda Civic, Sophie texted Seth, A woman thinks I'm queen of the dryads and has abducted me. Sophie's abductor looked placidly out the passenger window while the driver, a man around Sophie's age with dark brown curls not unlike Seth's, steered the car east to Amsterdam, then south. At...

Core promoter activity contributes to chromatin-based regulation of internal cryptic promoters.

During RNA polymerase II (RNA Pol II) transcription, the chromatin structure undergoes dynamic changes, including opening and closing of the nucleosome to enhance transcription elongation and fidelity. These changes are mediated by transcription elongation factors, including Spt6, the FACT complex, and the Set2-Rpd3S HDAC pathway. These factors not only contribute to RNA Pol II elongation, reset the repressive chromatin structures after RNA Pol II has passed, thereby inhibiting aberrant transcription initiation from the internal cryptic promoters within gene bodies. Notably, the internal cryptic promoters of infrequently transcribed genes are sensitive to such chromatin-based regulation but those of hyperactive genes are not. To determine why, the weak core promoters of genes that generate cryptic transcripts in cells lacking transcription elongation factors (e.g. STE11) were replaced with those from more active genes. Interestingly, as core promoter activity increased, activation of internal cryptic promoter dropped. This associated with loss of active histone modifications at the internal cryptic promoter. Moreover, environmental changes and transcription elongation factor mutations that downregulated the core promoters of highly active genes concomitantly increased their cryptic transcription. We therefore propose that the chromatin-based regulation of internal cryptic promoters is mediated by core promoter strength as well as transcription elongation factors.

Relationship between Core Strength, Core Endurance and Balance in Folk Dancers – A Pilot Study

Background: Dance performance requires lower extremity muscle strength and endurance, sufficientcore stabilization, dynamic balance during dance movements. Diminished core strength and coreendurance has been shown lead to a higher incidence of lower extremity injuries and to low backinjuries. Greater core muscle strength, increased core endurance and good dynamic balance havebeen reported to be associated with reduced lower extremity injury risk. Still, the exact relationshipsamong these factors remain unclear. Most of studies have examined ballet and modern dancers but folkdance is not studied adequately in the literature as different genres of dance have different physicaldemands, it is important to examine whether the relationships among Core stability, balance, injuries,and performance are similar across the various dance genres.Objectives: Weak core and poor balance are said to be associated with lower limb and low back injuries.Thus the correlation between core stabilization and balance need to be evaluated in details to reducethe risk of injuries.Methods: It is a cross-sectional observational study, with a total of 30 folk dancers. Core endurancewas measured by using plank tests and core strength was measured by the Bent Knee Lowering Test(BKLT).Balance was measured via the Star Excursion Balance Test (SEBT) which was co-related withcore strength and core endurance.Conclusion: There is no correlation between core strength and balance in folk dancers. Core enduranceis weakly correlated with balance.

A highly crystalline non-fullerene acceptor enabling efficient indoor organic photovoltaics with high EQE and fill factor

<h2>Summary</h2> The growth of the internet of things (IoT) is creating a demand for convenient energy sources, like organic photovoltaics, to power various small IoT devices. Here, we report a highly crystalline small molecular acceptor (named FCC-Cl) with an optical band gap of 1.71 eV suitable for indoor applications. The important design rationale of FCC-Cl is the combination of a weak electron-donating core and a moderate electron-withdrawing end group, which leads to needed band gap and high crystallinity. The OPVs based on D18:FCC-Cl achieved a high external quantum efficiency up to 85% and a high fill factor of 80% due to the high absorption coefficient and strong crystallinity of FCC-Cl. Consequently, an impressive power conversion efficiency of 28.8% was achieved under a 2,600 K LED lamp at 500 lux. It was also demonstrated that PM6:FCC-Cl-based devices can achieve high efficiencies over a wide range of active-layer thicknesses, which is a feature necessary for large-scale roll-to-roll printing processes.

A core stabilization program improves motor performance and health-related quality of life in adolescents with motor difficulties

Background: Developmental coordination disorder (DCD) is a neurodevelopmental condition characterized by poor motor competence that affects negatively adolescents’ activities of daily living and also pose an increased risk to their health and psychosocial development. Core stability improves posture, balance and proprioception, skills in which adolescents with DCD are deficient. A weak core is a fundamental problem in the inefficient production of motion, which can lead to incorrect motor patterns. Purpose: The aim of this study was to investigate the effectiveness of a core-stability functional exercise program on motor competence, health-related physical fitness, weekly physical activity and health-related quality of life (HRQoL) in adolescents with motor difficulties. Methods: 24 adolescents (12.75±.74y) participated in a 12 weeks (3 sessions/week) core-stability functional exercise program. Two groups were formed: experimental (DCDexp N=8) and control group (DCDcontrol N=16). Motor performance, balance, abdominal muscles strength/endurance, flexibility of lower back and hamstrings muscles, BMI, weekly physical activity and HRQoL were assessed pre and post intervention. Results: There were significant increases on motor performance, on balance, on abdominal muscles strength/endurance and on lower back and hamstrings muscles flexibility. Also, HRQoL and functional status were increased. There was no impact on physical activity and BMI. Conclusion: A core-stability functional exercise program seems to improve motor performance, health-related physical fitness, and HRQoL in adolescents with motor difficulties. This study provides evidence to the findings of the process-oriented approaches combined with effects in various parameters that guarantee success for these adolescents with poor motor competence.

FUGIN hot core survey. I. Survey method and initial results for l = 10°–20°

Abstract We have developed a method to make a spectral-line-based survey of hot cores, which represent an important stage of high-mass star formation, and applied the method to the data of the FUGIN (FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope) survey. First, we select hot core candidates by searching the FUGIN data for the weak hot core tracer lines (HNCO and CH3CN) by stacking, and then we conduct follow-up pointed observations on these candidates in C34S, SO, OCS, HC3N, HNCO, CH3CN, and CH3OH J = 2–1 and J = 8–7 lines to confirm and characterize them. We applied this method to the l = 10°–20° portion of the FUGIN data and identified 22 “HotCores” (compact sources with more than two significant detections of the hot core tracer lines, i.e., SO, OCS, HC3N, HNCO, CH3CN, or CH3OH J = 8–7 lines) and 14 “DenseClumps” (sources with more than two significant detection of C34S, CH3OH J = 2–1, or the hot core tracer lines). The identified HotCores are found to be associated with signposts of high-mass star formation such as ATLASGAL clumps, WISE H ii regions, and Class II methanol masers. Many of the FUGIN HotCores are identified with the Herschel Hi-GAL clumps with a median mass of 6.8 × 102 M⊙ and a median bolometric luminosity of 7.4 × 103 L⊙. Five of the seven HotCores with stronger CH3CN lines exhibit elevated gas temperatures of 50–100 K. These observations suggest that FUGIN HotCores are closely related to the formation of stars with medium to high mass. For those associated with ATLASGAL clumps, their bolometric luminosity to clump mass ratios are consistent with the star formation stages centered at the hot core phase. The catalog of FUGIN HotCores provides a useful starting point for further statistical studies and detailed observations of high-mass star forming regions.

Weighted weak core inverse of operators

As solutions of some operator equations, we present two new outer inverses for bounded linear operators between two Hilbert spaces. Precisely, we introduce and characterize the weighted weak core inverse and the dual weighted weak core inverse. These generalized inverses are extensions of the weak core inverse and its dual which have been recently introduced for complex square matrices. Also, we give various representations for the new inverses including operator matrix representations and the most general form. Applying our results, we define and investigate the weak core inverse and the dual weak core inverse for Hilbert spaces operators.

Comparison of the Isometric Hip Flexors Strength in Supine Position in Subjects With and Without Weak Isometric Core Strength

Background: Hip flexor muscles are very important in the hip joint structure as a mover and stabilizer. In addition, isometric hip flexor strength in the supine position needs to be considered with isometric core strength (WICS) to measure a precise strength in a clinical way. Objects: We compared isometric hip flexor strength in the supine position in subjects with and without WICS (between factors) and conditions with and without an external support (within factors). Methods: A total of 34 subjects (16 with WICS, 18 without WICS) participated in this study. We used the double-bent leg-lowering test to divide the subjects in two groups according to the presence of WICS. Isometric hip flexor strength was evaluated in the supine position both with and without an external support condition. The two-way mixed analysis of variance was applied to identify significant differences between groups (with vs. without WICS: between factors) and conditions (with vs. without an external support: within factors). Statistical significance was set at α = 0.05. Results: In subjects with WICS, isometric hip flexor strength was greater with an external support than without it (p = 0.0064). In subjects without WICS, there were no significant differences in isometric hip flexor strength in the presence or absence of an external support (p = 0.075). The isometric hip flexor strength was significantly greater with an external support condition in particular in subjects with WICS. Conclusion: The findings of this study reported that an external support condition in individuals with WICS may contribute to the improvement of isometric hip flexion strength in the supine position. Therefore, isometric core strength should be evaluated to distinguish the weakness between core region and hip flexors.

Full Implementation under Ambiguity

This paper introduces the maxmin expected utility framework into the problem of fully implementing a social choice set as ambiguous equilibria. Our model incorporates the Bayesian framework and the Wald-type maxmin preferences as special cases and provides insights beyond the Bayesian implementation literature. We establish necessary and almost sufficient conditions for a social choice set to be fully implementable. Under the Wald-type maxmin preferences, we provide easy-to-check sufficient conditions for implementation. As applications, we implement the set of ambiguous Pareto-efficient and individually rational social choice functions, the maxmin core, the maxmin weak core, and the maxmin value. (JEL D71, D81, D82)

Representations for the weak group inverse

The aim of this paper is to provide new representations and characterizations of the weak group inverse. We give a relation between the weak group inverse and a corresponding nonsingular border matrix. Continuity of weak group inverse is studied. Several limit representations, integral representations and perturbation formulae for the weak group inverse are proposed. Various expressions for the weak group and core–EP inverses of upper block triangular matrix are established and their sign patterns are considered. The splitting method for finding weak group inverse is proved as well as the successive matrix squaring algorithm for computing weak group inverse. Also, the weak group inverse can be used in solving appropriate systems of linear equations.

Impact of symmetry-breaking of non-fullerene acceptors for efficient and stable organic solar cells.

The concurrent enhancement of short-circuit current (JSC) and open-circuit voltage (VOC) is a key problem in the preparation of efficient organic solar cells (OSCs). In this paper, we report efficient and stable OSCs based on an asymmetric non-fullerene acceptor (NFA) IPC-BEH-IC2F. The NFA consists of a weak electron-donor core dithienothiophen[3,2-b]-pyrrolobenzothiadiazole (BEH) and two kinds of strong electron-acceptor (A) units [9H-indeno[1,2-b]pyrazine-2,3-dicarbonitrile (IPC) with a tricyclic fused system and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (IC2F)]. For comparison, the symmetric NFAs IPC-BEH-IPC and IC2F-BEH-IC2F were characterised. The kind of flanking A unit significantly affects the light absorption features and electronic structures of the NFAs. The asymmetric IPC-BEH-IC2F has the highest extinction coefficient among the three NFAs owing to its strong dipole moment and highly crystalline feature. Its highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels lie between those of the IPC-BEH-IPC and IC2F-BEH-IC2F molecules. The IPC group also promotes molecular packing through the tricyclic π-conjugated system and achieves increased crystallinity compared to that of the IC2F group. Inverted-type photovoltaic devices based on p-type polymer:NFA blends with PBDB-T and PM6 polymers as p-type polymers were fabricated. Among all these devices, the PBDB-T:IPC-BEH-IC2F blend device displayed the best photovoltaic properties because the IPC unit provides balanced electronic and morphological characteristics. More importantly, the PBDB-T:IPC-BEH-IC2F-based device exhibited the best long-term stability owing to the strongly interacting IPC moiety and the densely packed PBDB-T:IPC-BEH-IC2F film. These results demonstrate that asymmetric structural modifications of NFAs are an effective way for simultaneously improving the photovoltaic performance and stability of OSCs.

Infantile Blount disease: a developmental tibial growth defect.

A 2.5 years male child, who presented with Leg bowing. As per the parents, infant started walking early at 10th month and bowing of legs got worsened over time. Paediatric orthopedicians diagnosed him with endochondral disorder of the proximal end of medial tibial physis. He was referred to Physiotherapy department, for evaluation and rehabilitation. On examination, genu varum was seen (A), a positive ‘cover-up test´, internal tibial torsion, leg length difference, no tenderness, limitation of motion, and effusion, according to the review which lead to the diagnosis Blount's Disease. Lower extremity deformities in Rickets can closely mimic and osteochondro-dysplasia or genetic bone diseases which can cause lower extremity deformities similar to Blount's disease. The metaphyseal-diaphyseal angle of bones was determined and found to be 24°, which is considered abnormal. The child's lower leg was seen turned inward, causing the leg to appear bent below the knee (B). He had difficulties during walking and complained of pain in both the knees after 5-7 minutes of walk with lateral thrust on walking. According to Langenskiold Classification, the child is in stage 2 (2.5-4 yrs. old). As a result, parents were introduced to a home exercise program which included strengthening and stretching to correct gait and muscle imbalances, flexibility, as weak hip and core muscles contribute to knee deformities, and range of motion, which eases physical tasks and can benefit in the regression of secondary compensatory deformities, as well as Gait re-education through assistive devices (walker) improved the child's gait parameters.

Molecular Electron Acceptor Designed by Modulating Quinoidal-Resonance Effect for Organic Solar Cell Application

Abstract In this work, two new low-bandgap electron acceptors NITI-SeS and NITI-SSe that use electron-rich 2-alkylselenopheno[3,4-b]thiophene and 2-alkylselenopheno[2,3-c]thiophene with different quinoidal-resonance effect as π-bridges to link the weak electron-donating indenoindene core and the strong electron-accepting INCN-2F terminal are designed and synthesized. NITI-SeS that has a selenium atom in the main ring shows an obviously redshift absorption, leading to a low optical bandgap of 1.46 eV in thin film. By matching two acceptors with the polymer donor PBDB-T, the NITI-SSe-based device delivered a higher PCE of 12.49% with an open-circuit voltage of 0.91 V, a short-circuit current of 19.41 mA cm−2, and a fill factor of 0.70. This work reveals a convenient but effective method to finely tune the bandgap of non-fullerene acceptors for high-efficiency OSCs.

Characterization of the Weak Core of Simple Games with Infinitely Many Alternatives

We show that the characterization result of the weak core correspondence in simple games in Takamiya et al. (2018) still holds true even when the set of alternatives contains uncountably infinite elements.

Particle-in-cell Simulations of Secondary Magnetic Islands: Ion-scale Flux Ropes and Plasmoids

Abstract Ion-scale flux ropes and plasmoids are secondary magnetic islands produced during magnetic reconnection in various heliospheric plasma environments. Here we study the structure of secondary islands and the particle dynamics within them using particle-in-cell simulations. Ion-scale flux ropes (secondary islands with a strong core field) are formed in a strong guide field regime, whereas ion-scale plasmoids (secondary islands with a weak core field) are formed in a weak guide field regime. Currents in both types of secondary islands are carried primarily by electrons. Both types of secondary islands have a magnetic tension force pointing radially inward toward their center. In the flux rope type, this inward tension force is balanced by an outward magnetic pressure gradient of the strong core field; in the plasmoid type, it is countered by an outward thermal pressure gradient caused by electron and ion energizations. The transition between these two types occurs when B g /B 0 = 0.1–0.2 (B g is the guide field, and B 0 is the asymptotic magnetic field).

The weak core inverse

In this paper, we introduce a new generalized inverse, called weak core inverse (or, in short, WC inverse) of a complex square matrix. This new inverse extends the notion of the core inverse defined by Baksalary and Trenkler (Linear Multilinear Algebra 58(6):681–697, 2010). We investigate characterizations, representations, and properties for this generalized inverse. In addition, we introduce weak core matrices (or, in short, WC matrices) and we show that these matrices form a more general class than that given by the known weak group matrices, recently investigated by H. Wang and X. Liu.

Structural analysis and strength-to-weight optimization of wood-based sandwich composite with honeycomb core under three-point flexural test

Wood-based sandwich composite with a paper honeycomb core, especially for thick boards, has the advantage of high strength-to-weight ratio for the use in lightweight furniture products, interior walls etc. Employing both theoretical and experimental methods, this study investigated the influencing factors of various failure modes and its transition to obtain optimized structural parameters after a quasi-static load was applied. The results reveal that the skins of MDF are too strong for the paper honeycomb core. Both failure modes are caused by weak core properties. If the thickness or strength of the skins could be reduced or the core strength could be reinforced, then optimal failure mode of simultaneous core and skin failure could be reached. The intersection point of three transition lines is the best combination of structural parameters, meaning highest strength-to-weight ratio. At this point, failure of core shear, indentation and face fracture occurs simultaneously. The distance from a structural parameter to intersection is an effective index to express the degree of optimization for the strength-to-weight ratio of composites. Specimens close to the intersection point have optimal structural parameters and high strength-to-weight ratio. On application level, the optimum strength-to-weight ratio could be obtained easily by adjusting the surface or core thickness, if the materials were fixed first.