Multiscale mechanics of graphene oxide and graphene based composite films

NASA Astrophysics Data System (ADS)

Cao, Changhong

The mechanical behavior of graphene oxide is length scale dependent: orders of magnitude different between the bulk forms and monolayer counterparts. Understanding the underlying mechanisms plays a significant role in their versatile application. A systematic multiscale mechanical study from monolayer to multilayer, including the interactions between layers of GO, can provide fundamental support for material engineering. In this thesis, an experimental coupled with simulation approach was used to study the multiscale mechanics of graphene oxide (GO) and the methods developed for GO study are proved to be applicable also to mechanical study of graphene based composites. GO is a layered nanomaterial comprised of hierarchical units whose characteristic dimension lies between monolayer GO (0.7 nm - 1.2 nm) and bulk GO papers (≥ 1 mum). Mechanical behaviors of monolayer GO and GO nanosheets (10 nm- 100 nm) were comprehensively studied this work. Monolayer GO was measured to have an average strength of 24.7 GPa,, orders of magnitude higher than previously reported values for GO paper and approximately 50% of the 2D intrinsic strength of pristine graphene. The huge discrepancy between the strength of monolayer GO and that of bulk GO paper motivated the study of GO at the intermediate length scale (GO nanosheets). Experimental results showed that GO nanosheets possess high strength in the gigapascal range. Molecular Dynamic simulations showed that the transition in the failure behavior from interplanar fracture to intraplanar fracture was responsible for the huge strength discrepancy between nanometer scale GO and bulk GO papers. Additionally, the interfacial shear strength between GO layers was found to be a key contributing factor to the distinct mechanical behavior among hierarchical units of GO. The understanding of the multiscale mechanics of GO is transferrable in heterogeneous layered nanomaterials, such as graphene-metal oxide based anode materials in Li-ion batteries. The novel methods developed in this work to study GO multilayered structures were also applied to study the mechanics of graphene-TiO 2 composites. It was found that a critical thickness range of TiO2 deposition on graphene is required for the observed stiffness enhancement effect of graphene to influence the mechanical behavior of the composite.

How Do Apps Work? An Analysis of Physical Activity App Users' Perceptions of Behavior Change Mechanisms.

PubMed

Hoj, Taylor H; Covey, Emarie L; Jones, Allyn C; Haines, Amanda C; Hall, P Cougar; Crookston, Benjamin T; West, Joshua H

2017-08-03

Physical activity apps are commonly used to increase levels of activity and health status. To date, the focus of research has been to determine the potential of apps to influence behavior, to ascertain the efficacy of a limited number of apps to change behavior, and to identify the characteristics of apps that users prefer. The purpose of this study was to identify the mechanisms by which the use of physical activity apps may influence the users' physical activity behavior. This study used a cross-sectional survey of users of health-related physical activity apps during the past 6 months. An electronic survey was created in Qualtrics' Web-based survey software and deployed on Amazon Mechanical Turk. Individuals who had used at least one physical activity app in the past 6 months were eligible to respond. The final sample comprised 207 adults living in the United States. 86.0% (178/207) of respondents were between the ages of 26 and 54 years, with 51.2% (106/207) of respondents being female. Behavior change theory informed the creation of 20 survey items relating to the mechanisms of behavior change. Respondents also reported about engagement with the apps, app likeability, and physical activity behavior. Respondents reported that using a physical activity app in the past 6 months resulted in a change in their attitudes, beliefs, perceptions, and motivation. Engagement with the app (P<.001), frequency of app use (P=.03), and app price (P=.01) were related to the reported impact of the behavior change theory or mechanisms of change. The mechanisms of change were associated with self-reported physical activity behaviors (P<.001). The findings from this study provide an overview of the mechanisms by which apps may impact behavior. App developers may wish to incorporate these mechanisms in an effort to increase impact. Practitioners should consider the extent to which behavior change theory is integrated into a particular app when they consider making recommendations to others wishing to increase levels of physical activity. ©Taylor H Hoj, Emarie L Covey, Allyn C Jones, Amanda C Haines, P Cougar Hall, Benjamin T Crookston, Joshua H West. Originally published in JMIR Mhealth and Uhealth (http://mhealth.jmir.org), 03.08.2017.

How do illness-anxious individuals process health-threatening information? A systematic review of evidence for the cognitive-behavioral model.

PubMed

Leonidou, Chrysanthi; Panayiotou, Georgia

2018-08-01

According to the cognitive-behavioral model, illness anxiety is developed and maintained through biased processing of health-threatening information and maladaptive responses to such information. This study is a systematic review of research that attempted to validate central tenets of the cognitive-behavioral model regarding etiological and maintenance mechanisms in illness anxiety. Sixty-two studies, including correlational and experimental designs, were identified through a systematic search of databases and were evaluated for their quality. Outcomes were synthesized following a qualitative thematic approach under categories of theoretically driven mechanisms derived from the cognitive-behavioral model: attention, memory and interpretation biases, perceived awareness and inaccuracy in perception of somatic sensations, negativity bias, emotion dysregulation, and behavioral avoidance. Findings partly support the cognitive-behavioral model, but several of its hypothetical mechanisms only receive weak support due to the scarcity of relevant studies. Directions for future research are suggested based on identified gaps in the existing literature. Copyright © 2018 Elsevier Inc. All rights reserved.

Contagious behavior: an alternative approach to mirror-like phenomena.

PubMed

Provine, Robert R

2014-04-01

Contagious behaviors such as yawning and itching/scratching have mirror-like properties and clearly defined stimulus and motor parameters; they are also relatively easy to study and should be part of the debate about mirror neurons and the neurological mechanisms of social behavior. The broadly tuned, multimodal stimuli of contagious behavior challenge present accounts of mirror mechanisms that focus on specific, mirrored acts.

Mechanisms of Song Perception in Oscine Birds

ERIC Educational Resources Information Center

Knudsen, Daniel P.; Gentner, Timothy Q.

2010-01-01

Songbirds share a number of parallels with humans that make them an attractive model system for studying the behavioral and neurobiological mechanisms that underlie the learning and processing of vocal communication signals. Here we review the perceptual and cognitive mechanisms of audition in birds, and emphasize the behavioral and neural basis…

The mechanical and electrochemical properties of bulk metallic glasses

NASA Astrophysics Data System (ADS)

Morrison, Mark Lee

The objectives of this study were to define and model the electrochemical and mechanical behaviors of BMGs, in addition to the interactions between these. The electrochemical behaviors of Zr-, Ti-, and Ca-based BMGs have been studied in various environments. Moreover, the electrochemical behaviors of several common, crystalline materials have also been characterized in the same environments to facilitate comparisons. Mechanical characterization of the Vitreloy 105 alloy was conducted through four-point bend fatigue testing, as well as tensile testing with in situ thermography. After the electrochemical and mechanical behaviors of the Vit 105 BMG alloy were defined separately, the corrosion-fatigue behavior of this alloy was studied. Corrosion-fatigue tests were conducted in a 0.6 M NaCl electrolyte, identical to one of the environments in which the electrochemical behavior was previously defined. The environmental effect was found to be significant at most stress levels, with decreasing effects at higher stress levels due to decreasing time in the detrimental environment, and severely depressed the corrosion-fatigue endurance limit. Cyclic-anodic-polarization tests were conducted during cyclic loading to elucidate the effect of cyclic stresses on the electrochemical behavior. It was found that a stress range of 900 MPa resulted in active pitting at the open-circuit potentials. The degradation mechanism was determined to be stress-assisted dissolution, not hydrogen embrittlement. Finally, tensile tests were conducted with the Vit 105 BMG alloy with in situ infrared (IR) thermography to observe the evolution of shear bands during deformation. More importantly, the length, location, sequence, temperature evolution, and velocity of individual shear bands have been quantified through the use of IR thermography. Based upon all of these studies on a variety of BMG alloy systems, the most important factor in the mechanical and electrochemical behavior was found to be material quality and homogeneity. Therefore, future research on the improvement of BMG alloys should be focused on this area.

Processing and Characterization of Cellulose Nanocrystals/Polylactic Acid Nanocomposite Films

Treesearch

Erin Sullivan; Robert Moon; Kyriaki Kalaitzidou

2015-01-01

The focus of this study is to examine the effect of cellulose nanocrystals (CNC) on the properties of polylactic acid (PLA) films. The films are fabricated via melt compounding and melt fiber spinning followed by compression molding. Film fracture morphology, thermal properties, crystallization behavior, thermo-mechanical behavior, and mechanical behavior were...

Influence of crosslinking on the mechanical behavior of 3D printed alginate scaffolds: Experimental and numerical approaches.

PubMed

Naghieh, Saman; Karamooz-Ravari, Mohammad Reza; Sarker, M D; Karki, Eva; Chen, Xiongbiao

2018-04-01

Tissue scaffolds fabricated by three-dimensional (3D) bioprinting are attracting considerable attention for tissue engineering applications. Because the mechanical properties of hydrogel scaffolds should match the damaged tissue, changing various parameters during 3D bioprinting has been studied to manipulate the mechanical behavior of the resulting scaffolds. Crosslinking scaffolds using a cation solution (such as CaCl 2 ) is also important for regulating the mechanical properties, but has not been well documented in the literature. Here, the effect of varied crosslinking agent volume and crosslinking time on the mechanical behavior of 3D bioplotted alginate scaffolds was evaluated using both experimental and numerical methods. Compression tests were used to measure the elastic modulus of each scaffold, then a finite element model was developed and a power model used to predict scaffold mechanical behavior. Results showed that crosslinking time and volume of crosslinker both play a decisive role in modulating the mechanical properties of 3D bioplotted scaffolds. Because mechanical properties of scaffolds can affect cell response, the findings of this study can be implemented to modulate the elastic modulus of scaffolds according to the intended application. Copyright © 2018 Elsevier Ltd. All rights reserved.

Aging and loading rate effects on the mechanical behavior of equine bone

NASA Astrophysics Data System (ADS)

Kulin, Robb M.; Jiang, Fengchun; Vecchio, Kenneth S.

2008-06-01

Whether due to a sporting accident, high-speed impact, fall, or other catastrophic event, the majority of clinical bone fractures occur under dynamic loading conditions. However, although extensive research has been performed on the quasi-static fracture and mechanical behavior of bone to date, few high-quality studies on the fracture behavior of bone at high strain rates have been performed. Therefore, many questions remain regarding the material behavior, including not only the loading-rate-dependent response of bone, but also how this response varies with age. In this study, tests were performed on equine femoral bone taken post-mortem from donors 6 months to 28 years of age. Quasi-static and dynamic tests were performed to determine the fracture toughness and compressive mechanical behavior as a function of age at varying loading rates. Fracture paths were then analyzed using scanning confocal and scanning-electron microscopy techniques to assess the role of various microstructural features on toughening mechanisms.

Impact of formulation and saliva on acid milk gel friction behavior.

PubMed

Joyner Melito, Helen S; Pernell, Chris W; Daubert, Christopher R

2014-05-01

Rheological analysis is commonly used to evaluate mechanical properties in studies of food behavior. However, rheological analysis is often insufficient to describe food texture as evaluated by descriptive sensory analysis. Additionally, traditional rheometry does not account for changes in food behavior as a function of saliva incorporation into the food during mastication. The objectives of this study were to evaluate friction behavior of acid milk gels with and without the addition of saliva, and to determine relationships between frictional behaviors and mechanical and sensory behaviors. Acid milk gels were prepared with 12.5% total solids comprising nonfat dry milk, whey protein isolate, waxy maize starch, and gelatin in different ratios. The addition of starch was found to have significant impact on acid milk gel frictional behavior. Addition of saliva resulted in a change in frictional behavior over the entire sliding speed range measured. Correlations were found between rheological, tribological, and sensory behavior, suggesting that an underlying mechanism may impact both viscosity and friction behavior. Additional study is needed to further explore the links between food structure, rheology, tribology, and sensory texture. Application of tribology in food science allows measurement of friction behavior of foods. Matching both rheological and tribological behavior is important to creating reduced-fat or reduced-sugar products with similar mouthfeel to the original product. © 2014 Institute of Food Technologists®

Behavioral genetics and taste

PubMed Central

Boughter, John D; Bachmanov, Alexander A

2007-01-01

This review focuses on behavioral genetic studies of sweet, umami, bitter and salt taste responses in mammals. Studies involving mouse inbred strain comparisons and genetic analyses, and their impact on elucidation of taste receptors and transduction mechanisms are discussed. Finally, the effect of genetic variation in taste responsiveness on complex traits such as drug intake is considered. Recent advances in development of genomic resources make behavioral genetics a powerful approach for understanding mechanisms of taste. PMID:17903279

Characterization of the anisotropic mechanical behavior of human abdominal wall connective tissues.

PubMed

Astruc, Laure; De Meulaere, Maurice; Witz, Jean-François; Nováček, Vit; Turquier, Frédéric; Hoc, Thierry; Brieu, Mathias

2018-06-01

Abdominal wall sheathing tissues are commonly involved in hernia formation. However, there is very limited work studying mechanics of all tissues from the same donor which prevents a complete understanding of the abdominal wall behavior and the differences in these tissues. The aim of this study was to investigate the differences between the mechanical properties of the linea alba and the anterior and posterior rectus sheaths from a macroscopic point of view. Eight full-thickness human anterior abdominal walls of both genders were collected and longitudinal and transverse samples were harvested from the three sheathing connective tissues. The total of 398 uniaxial tensile tests was conducted and the mechanical characteristics of the behavior (tangent rigidities for small and large deformations) were determined. Statistical comparisons highlighted heterogeneity and non-linearity in behavior of the three tissues under both small and large deformations. High anisotropy was observed under small and large deformations with higher stress in the transverse direction. Variabilities in the mechanical properties of the linea alba according to the gender and location were also identified. Finally, data dispersion correlated with microstructure revealed that macroscopic characterization is not sufficient to fully describe behavior. Microstructure consideration is needed. These results provide a better understanding of the mechanical behavior of the abdominal wall sheathing tissues as well as the directions for microstructure-based constitutive model. Copyright © 2018 Elsevier Ltd. All rights reserved.

An Examination of the Mechanisms of Action in Cognitive Behavioral Therapy for Bulimia Nervosa

ERIC Educational Resources Information Center

Spangler, Diane L.; Baldwin, Scott A.; Agras, W. Stewart

2004-01-01

Cognitive-behavioral therapy (CBT) for bulimia nervosa (BN) has received considerable empirical support for its efficacy. However, few investigators have examined the mechanisms proposed to account for the reduction of BN symptoms during CBT. The current study examined the associations between therapist interventions, client mechanisms, and…

Investigations into the mechanical and physical behavior of thermoplastic elastomers

NASA Astrophysics Data System (ADS)

Wright, Kathryn Janelle

This thesis describes investigations into the physical and mechanical characteristics of two commercial thermoplastic elastomer (TPE) systems. Both systems studied exhibit elastomeric behavior similar to more traditional crosslinked elastomers; however, in these TPEs non-conventional polymer architectures and morphologies are used to produce their elastomeric behavior. The two TPEs of interest are ethylene-propylene random copolymers and dynamically vulcanized blends of ethylene-propylene-diene monomer (EPDM) and isotactic polypropylene (iPP). Very few studies have examined the mechanical behavior of these materials in terms of their composition and morphology. As such, the primary goal of this research is to both qualitatively and quantitatively understand the influence of composition and morphology on mechanical behavior. In additional very little information is available that compares their performance with that of crosslinked elastomers. As a result, the secondary goal is to qualitatively compare the mechanical responses of these TPEs with that of their more traditional counterparts. The ethylene-propylene copolymers studied have very high comonomer contents and exhibit slow crystallization kinetics. Their morphology consists of nanoscale crystallites embedded in an amorphous rubbery matrix. These crystallites act as physical crosslinks that allow for elasticity. Slow crystallization causes subsequent changes in mechanical behavior that take place over days and even weeks. Physical responses (e.g., density, crystallization kinetics, and crystal structure) of five copolymer compositions are investigated. Mechanical responses (e.g., stiffness, ductility, yielding, and reversibility) are also examined. Finally, the influence of morphology on deformation is studied using in situ analytical techniques. The EPDM/iPP blends are dynamically vulcanized which produces a complex morphology consisting of chemically crosslinked EPDM domains embedded within a semicrystalline iPP matrix. Six compositions are investigated as a function of three parameters: major volume fraction, iPP molecular weight, and EPDM cure state. The influence of these parameters on morphology and resulting mechanical behavior is examined. This work culminates in the development of a morphological model to describe the steady-state reversibility of these EPDM/iPP blends. The model is then evaluated in terms of composition and cure state.

The ENGAGE study: Integrating neuroimaging, virtual reality and smartphone sensing to understand self-regulation for managing depression and obesity in a precision medicine model.

PubMed

Williams, Leanne M; Pines, Adam; Goldstein-Piekarski, Andrea N; Rosas, Lisa G; Kullar, Monica; Sacchet, Matthew D; Gevaert, Olivier; Bailenson, Jeremy; Lavori, Philip W; Dagum, Paul; Wandell, Brian; Correa, Carlos; Greenleaf, Walter; Suppes, Trisha; Perry, L Michael; Smyth, Joshua M; Lewis, Megan A; Venditti, Elizabeth M; Snowden, Mark; Simmons, Janine M; Ma, Jun

2018-02-01

Precision medicine models for personalizing achieving sustained behavior change are largely outside of current clinical practice. Yet, changing self-regulatory behaviors is fundamental to the self-management of complex lifestyle-related chronic conditions such as depression and obesity - two top contributors to the global burden of disease and disability. To optimize treatments and address these burdens, behavior change and self-regulation must be better understood in relation to their neurobiological underpinnings. Here, we present the conceptual framework and protocol for a novel study, "Engaging self-regulation targets to understand the mechanisms of behavior change and improve mood and weight outcomes (ENGAGE)". The ENGAGE study integrates neuroscience with behavioral science to better understand the self-regulation related mechanisms of behavior change for improving mood and weight outcomes among adults with comorbid depression and obesity. We collect assays of three self-regulation targets (emotion, cognition, and self-reflection) in multiple settings: neuroimaging and behavioral lab-based measures, virtual reality, and passive smartphone sampling. By connecting human neuroscience and behavioral science in this manner within the ENGAGE study, we develop a prototype for elucidating the underlying self-regulation mechanisms of behavior change outcomes and their application in optimizing intervention strategies for multiple chronic diseases. Copyright © 2017. Published by Elsevier Ltd.

A review of the deformation behavior of tungsten at temperatures less than 0.2 of the melting point /K/

NASA Technical Reports Server (NTRS)

Stephens, J. R.

1974-01-01

The deformation behavior of tungsten at temperatures below 0.2 times the absolute melting temperature is reviewed with primary emphasis on the temperature dependence of the yield stress and the ductile-brittle transition. It is concluded that a model based on the high Peierls stress of tungsten best accounts for the observed mechanical behavior at low temperatures. Recent research suggests an important role of electron concentration and bonding on the mechanical behavior of tungsten. Future research on tungsten should include studies to define more clearly the correlation between electron concentration and mechanical behavior of alloys of tungsten and other transition metal alloys.

Review of deformation behavior of tungsten at temperature less than 0.2 absolute melting temperature

NASA Technical Reports Server (NTRS)

Stephens, J. R.

1972-01-01

The deformation behavior of tungsten at temperatures 0.2 T sub m is reviewed, with primary emphasis on the temperature dependence of the yield stress and the ductile-brittle transition temperature. It appears that a model based on the high Peierls stress of tungsten best accounts for the observed mechanical behavior at low temperatures. Recent research is discussed which suggests an important role of electron concentration and bonding on the mechanical behavior of tungsten. It is concluded that future research on tungsten should include studies to define more clearly the correlation between electron concentration and mechanical behavior of tungsten alloys and other transition metal alloys.

The Effect of Parents’ Attitudes on Sons’ Marriage Timing

PubMed Central

Jennings, Elyse A.; Axinn, William G.; Ghimire, Dirgha J.

2012-01-01

Theories of family stability and change, demographic processes, and social psychological influences on behavior all posit that parental attitudes and beliefs are a key influence on their children’s behavior. Though we have evidence of these effects in Western populations, there is little information regarding this social mechanism in non-Western contexts. Furthermore, comparisons of mothers’ and fathers’ independent roles in these crucial intergenerational mechanisms are rare. This paper uses measures from a ten-year family panel study featuring independent interviews with both mothers and fathers in rural Nepal to investigate these issues. We test the association of specific attitudes, rather than broad ideational domains, about childbearing and old-age care with sons’ subsequent marriage behavior. Our results indicate that both mothers’ and fathers’ attitudes have important and independent influences on sons’ marriage behavior. Simultaneous study of both parents’ attitudes reveals that gender-specific parenting contexts can shape the relationship between parental attitudes and children’s behaviors. This crucial mechanism of intergenerational continuity and change is strong in this non-Western setting, with substantial implications for studies of intergenerational influences on behavior in all settings. PMID:23483623

Role of Polymer Segregation on the Mechanical Behavior of All-Polymer Solar Cell Active Layers.

PubMed

Balar, Nrup; Xiong, Yuan; Ye, Long; Li, Sunsun; Nevola, Daniel; Dougherty, Daniel B; Hou, Jianhui; Ade, Harald; O'Connor, Brendan T

2017-12-20

An all-polymer bulk heterojunction (BHJ) active layer that removes the use of commonly used small molecule electron acceptors is a promising approach to improve the thermomechanical behavior of organic solar cells. However, there has been limited research on their mechanical properties. Here, we report on the mechanical behavior of high-performance blade-coated all-polymer BHJ films cast using eco-friendly solvents. The mechanical properties considered include the elastic modulus, crack onset strain, and cohesive fracture energy. We show that the mechanical behavior of the blend is largely unaffected by significant changes in the segregation characteristics of the polymers, which was varied systematically through solvent formulation. In comparison to a polymer:fullerene BHJ counterpart, the all-polymer films were found to have lower stiffness and increased ductility. Yet, the fracture energy of the all-polymer films is not significantly improved compared to that of the polymer:fullerene films. This study highlights that improved mechanical behavior of all-polymer systems cannot be assumed, and that details of the molecular structure, molecular weight, and film morphology play an important role in both the optoelectronic and mechanical properties. Furthermore, we show that simple composite modeling provides a predictive tool for the mechanical properties of the polymer blend films, providing a framework to guide future optimization of the mechanical behavior.

Epigenetics: Behavioral Influences on Gene Function, Part II--Molecular Mechanisms

ERIC Educational Resources Information Center

Ogren, Marilee P.; Lombroso, Paul J.

2008-01-01

A study presented on the effect of parenting on stress response and other behaviors show that animals exposed to a high degree of nurturing show a blunted response to stress. Molecular mechanisms responsible for these differences in the adult offspring as well as the molecular mechanisms by which epigenetic effects are propagated from one…

Mechanical modeling of self-expandable stent fabricated using braiding technology.

PubMed

Kim, Ju Hyun; Kang, Tae Jin; Yu, Woong-Ryeol

2008-11-14

The mechanical behavior of a stent is one of the important factors involved in ensuring its opening within arterial conduits. This study aimed to develop a mechanical model for designing self-expandable stents fabricated using braiding technology. For this purpose, a finite element model was constructed by developing a preprocessing program for the three-dimensional geometrical modeling of the braiding structure inside stents, and validated for various stents with different braiding structures. The constituent wires (Nitinol) in the braided stents were assumed to be superelastic material and their mechanical behavior was incorporated into the finite element software through a user material subroutine (VUMAT in ABAQUS) employing a one-dimensional superelastic model. For the verification of the model, several braided stents were manufactured using an automated braiding machine and characterized focusing on their compressive behavior. It was observed that the braided stents showed a hysteresis between their loading and unloading behavior when a compressive load was applied to the braided tube. Through the finite element analysis, it was concluded that the current mechanical model can appropriately predict the mechanical behavior of braided stents including such hysteretic behavior, and that the hysteresis was caused by the slippage between the constituent wires and their superelastic property.

Modeling of Nonlinear Mechanical Response in CFRP Angle-Ply Laminates

NASA Astrophysics Data System (ADS)

Ogihara, Shinji

2014-03-01

It is known that the failure process in angle-ply laminate involves matrix cracking and delamination and that they exhibit nonlinear stress-strain relation. There may be a significant effect of the constituent blocked ply thickness on the mechanical behavior of angle-ply laminates. These days, thin prepregs whose thickness is, for example 50 micron, are developed and commercially available. Therefore, we can design wide variety of laminates with various constituent ply thicknesses. In this study, effects of constituent ply thickness on the nonlinear mechanical behavior and the damage behavior of CFRP angle-ply laminates are investigated experimentally. Based on the experimental results, the mechanical response in CFRP angle-ply laminates is modeled by using the finite strain viscoplasticity model. We evaluated the mechanical behavior and damage behavior in CFRP angle-ply laminates with different constituent ply thickness under tensile loading experimentally. It was found that as the constituent ply thickness decreases, the strength and failure strain increases. We also observed difference in damage behavior. The preliminary results of finite strain viscoplasticity model considering the damage effect for laminated composites are shown. A qualitative agreement is obtained.

Mechanisms by which childhood personality traits influence adult health status: educational attainment and healthy behaviors.

PubMed

Hampson, Sarah E; Goldberg, Lewis R; Vogt, Thomas M; Dubanoski, Joan P

2007-01-01

The purpose of this study was to test a life span health behavior model in which educational attainment and health behaviors (eating habits, smoking, and physical activity) were hypothesized as mechanisms to account for relations between teacher ratings of childhood personality traits and self-reported health status at midlife. The model was tested on 1,054 members of the Hawaii Personality and Health cohort, which is a population-based cohort participating in a longitudinal study of personality and health spanning 40 years from childhood to midlife. Childhood Agreeableness, Conscientiousness, and Intellect-Imagination influenced adult health status indirectly through educational attainment, healthy eating habits, and smoking. Several direct effects of childhood traits on health behaviors and health status were also observed. The model extends past associations found between personality traits and health behaviors or health status by identifying a life-course pathway based on the health behavior model through which early childhood traits influence adult health status. The additional direct effects of personality traits indicate that health behavior mechanisms may not provide a complete account of relations between personality and health.

Size-dependent fracture behavior of silver nanowires.

PubMed

Cao, Ke; Han, Ying; Zhang, Hongti; Gao, Libo; Yang, Hongwei; Chen, Jialin; Li, Yuxiu; Lu, Yang

2018-07-20

Silver (Ag) nanowires have great potential to be used in the flexible electronics industry for their applications in flexible, transparent conductors due to high conductivity and light reflectivity. Those applications always involve mechanical loading and deformations, which requires an in-depth understanding of their mechanical behavior and performance under loadings. However, current understanding on the mechanical properties of Ag nanowires is limited, especially on their size-dependent fracture behavior. In this work, mechanical properties of Ag nanowires with diameters ranging from 50 to 300 nm were systematically studied by in situ TEM tensile testing for the first time. The size effect was clearly found, with the increasing of the diameter of Ag nanowires, the ultimate tensile stress decreased. More importantly, the fracture behavior of Ag nanowire was studied and a brittle-to-ductile transition in fracture behavior was observed at the diameters around 100 nm which could be attributed to the dislocation activities within the geometry confinement. This work could give insights for understanding nanosized Ag wires and the design of Ag nanowire-based flexible devices and touchable panels.

Size-dependent fracture behavior of silver nanowires

NASA Astrophysics Data System (ADS)

Cao, Ke; Han, Ying; Zhang, Hongti; Gao, Libo; Yang, Hongwei; Chen, Jialin; Li, Yuxiu; Lu, Yang

2018-07-01

Silver (Ag) nanowires have great potential to be used in the flexible electronics industry for their applications in flexible, transparent conductors due to high conductivity and light reflectivity. Those applications always involve mechanical loading and deformations, which requires an in-depth understanding of their mechanical behavior and performance under loadings. However, current understanding on the mechanical properties of Ag nanowires is limited, especially on their size-dependent fracture behavior. In this work, mechanical properties of Ag nanowires with diameters ranging from 50 to 300 nm were systematically studied by in situ TEM tensile testing for the first time. The size effect was clearly found, with the increasing of the diameter of Ag nanowires, the ultimate tensile stress decreased. More importantly, the fracture behavior of Ag nanowire was studied and a brittle-to-ductile transition in fracture behavior was observed at the diameters around 100 nm which could be attributed to the dislocation activities within the geometry confinement. This work could give insights for understanding nanosized Ag wires and the design of Ag nanowire-based flexible devices and touchable panels.

Adolescent Suicidal Behavior and Substance Use: Developmental Mechanisms

PubMed Central

Dawes, Michael A; Mathias, Charles W; Richard, Dawn M; Hill-Kapturczak, Nathalie; Dougherty, Donald M

2008-01-01

Adolescent suicidal behaviors and substance use are disturbingly common. Research suggests overlap of some of the etiological mechanisms for both adolescent suicidal behavior and substance use, yet clear understanding of the complex relations between these behaviors and their causal underpinnings is lacking. A growing body of evidence and a diathesis model (Mann et al. 1999; Mann, 2003) highlight the importance of impulse control as a proximal risk factor for adolescent suicidal and substance use behaviors. This literature review extends current theory on the relationships between adolescent suicidal behavior and substance use by: (1) examining how, when, and to what extent adolescent development is affected by poor impulse control, stressful life events, substance use behavior, and biological factors; (2) presenting proposed causal mechanisms by which these risk factors interact to increase risk for suicidal behaviors and substance use; and (3) proposing specific new hypotheses to extend the diathesis model to adolescents at risk for suicide and substance use. More specifically, new hypotheses are presented that predict bidirectional relationships between stressful life events and genetic markers of 5-HT dysregulation; substance use behavior and impulsivity; and substance use behavior and suicide attempts. The importance of distinguishing between different developmental trajectories of suicidal and substance use behaviors, and the effects of specific risk and protective mechanisms are discussed. Use of new statistical approaches that provide for the comparison of latent growth curves and latent class models is recommended to identify differences in developmental trajectories of suicidal behavior and substance use. Knowledge gained from these prospective longitudinal methods should lead to greater understanding on the timing, duration, and extent to which specific risk and protective factors influence the outcomes of suicidal behavior and substance use. In turn, findings from these studies should inform researchers who conduct future treatment and prevention studies. PMID:20651946

The Effect of Cognitive Behavioral Therapy (CBT) on Depression: The Role of Problem-Solving Appraisal

ERIC Educational Resources Information Center

Chen, Szu-Yu; Jordan, Catheleen; Thompson, Sanna

2006-01-01

Objective: Many studies have confirmed the efficacy of cognitive behavioral therapy (CBT) as a treatment for depression. However, the mechanism of CBT for depression reduction is still not well understood. This study explored the mechanism of CBT from the perspective of individuals' problem-solving appraisal. Method: A one-group pretest-posttest…

Cellular Analogs of Operant Behavior.

DTIC Science & Technology

1992-07-31

confirmed at the behavioral level in parallel studies of hippocampal and intravenous self-administration. The results are consistent with the hypothesis...research is to elucidate the cellular reinforcement mechanisms underlying goal-directed or operant behavior. The specific aim here was to study the... studies and behavioral operant conditioning studies . Most of the research reported was initiated and completed in the present project period. Also

Nurse and patient interaction behaviors' effects on nursing care quality for mechanically ventilated older adults in the ICU.

PubMed

Nilsen, Marci L; Sereika, Susan M; Hoffman, Leslie A; Barnato, Amber; Donovan, Heidi; Happ, Mary Beth

2014-01-01

The study purposes were to (a) describe interaction behaviors and factors that may effect communication and (b) explore associations between interaction behaviors and nursing care quality indicators among 38 mechanically ventilated patients (age ≥60 years) and their intensive care unit nurses (n = 24). Behaviors were measured by rating videorecorded observations from the Study of Patient-Nurse Effectiveness with Communication Strategies (SPEACS). Characteristics and quality indicators were obtained from the SPEACS dataset and medical chart abstraction. All positive behaviors occurred at least once. Significant (p < 0.05) associations were observed between (a) positive nurse and positive patient behaviors, (b) patient unaided augmentative and alternative communication (AAC) strategies and positive nurse behaviors, (c) individual patient unaided AAC strategies and individual nurse positive behaviors, (d) positive nurse behaviors and pain management, and (e) positive patient behaviors and sedation level. Findings provide evidence that nurse and patient behaviors effect communication and may be associated with nursing care quality. Copyright 2014, SLACK Incorporated.

Nurse and Patient Interaction Behaviors Effects on Nursing Care Quality for Mechanically Ventilated, Older Adults in the ICU

PubMed Central

Nilsen, Marci; Sereika, Susan M.; Hoffman, Leslie A.; Barnato, Amber; Donovan, Heidi; Happ, Mary Beth

2014-01-01

The study purposes were to 1) describe interaction behaviors and factors that may impact communication and 2) explore associations between interaction behaviors and nursing care quality indicators between 38 mechanically ventilated patients (≥60 years) and their intensive care unit nurses (n=24). Behaviors were measured by rating videotaped observations from the Study of Patient-Nurse Effectiveness with Communication Strategies (SPEACS). Characteristics and quality indicators were obtained from the SPEACS dataset and medical chart abstraction. All positive behaviors occurred at least once. Significant (p<.05) associations were observed between: 1) positive nurse and positive patient behaviors, 2) patient unaided augmentative and alternative communication (AAC) strategies and positive nurse behaviors, 3) individual patient unaided AAC strategies and individual nurse positive behaviors and 4) positive nurse behaviors and pain management, and 5) positive patient behaviors and sedation level. Findings provide evidence that nurse and patient behaviors impact communication and may be associated with nursing care quality. PMID:24496114

Experiments and Simulations of Fully Hydro-Mechanically Coupled Response of Rough Fractures Exposed to High-Pressure Fluid Injection

NASA Astrophysics Data System (ADS)

Vogler, D.; Settgast, R. R.; Annavarapu, C.; Madonna, C.; Bayer, P.; Amann, F.

2018-02-01

In this work, we present the application of a fully coupled hydro-mechanical method to investigate the effect of fracture heterogeneity on fluid flow through fractures at the laboratory scale. Experimental and numerical studies of fracture closure behavior in the presence of heterogeneous mechanical and hydraulic properties are presented. We compare the results of two sets of laboratory experiments on granodiorite specimens against numerical simulations in order to investigate the mechanical fracture closure and the hydro-mechanical effects, respectively. The model captures fracture closure behavior and predicts a nonlinear increase in fluid injection pressure with loading. Results from this study indicate that the heterogeneous aperture distributions measured for experiment specimens can be used as model input for a local cubic law model in a heterogeneous fracture to capture fracture closure behavior and corresponding fluid pressure response.

Review: mechanical behavior of metal/ceramic interfaces in nanolayered composites—experiments and modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Nan; Liu, Xiang-Yang

In this study, recent experimental and modeling studies in nanolayered metal/ceramic composites are reviewed, with focus on the mechanical behaviors of metal/nitrides interfaces. The experimental and modeling studies of the slip systems in bulk TiN are reviewed first. Then, the experimental studies of interfaces, including co-deformation mechanism by micropillar compression tests, in situ TEM straining tests for the dynamic process of the co-deformation, thickness-dependent fracture behavior, and interrelationship among the interfacial bonding, microstructure, and mechanical response, are reviewed for the specific material systems of Al/TiN and Cu/TiN multilayers at nanoscale. The modeling studies reviewed cover first-principles density functional theory-based modeling,more » atomistic molecular dynamics simulations, and mesoscale modeling of nanolayered composites using discrete dislocation dynamics. The phase transformation between zinc-blende and wurtzite AlN phases in Al/AlN multilayers at nanoscale is also reviewed. Finally, a summary and perspective of possible research directions and challenges are given.« less

Review: mechanical behavior of metal/ceramic interfaces in nanolayered composites—experiments and modeling

DOE PAGES

Li, Nan; Liu, Xiang-Yang

2017-11-03

In this study, recent experimental and modeling studies in nanolayered metal/ceramic composites are reviewed, with focus on the mechanical behaviors of metal/nitrides interfaces. The experimental and modeling studies of the slip systems in bulk TiN are reviewed first. Then, the experimental studies of interfaces, including co-deformation mechanism by micropillar compression tests, in situ TEM straining tests for the dynamic process of the co-deformation, thickness-dependent fracture behavior, and interrelationship among the interfacial bonding, microstructure, and mechanical response, are reviewed for the specific material systems of Al/TiN and Cu/TiN multilayers at nanoscale. The modeling studies reviewed cover first-principles density functional theory-based modeling,more » atomistic molecular dynamics simulations, and mesoscale modeling of nanolayered composites using discrete dislocation dynamics. The phase transformation between zinc-blende and wurtzite AlN phases in Al/AlN multilayers at nanoscale is also reviewed. Finally, a summary and perspective of possible research directions and challenges are given.« less

Neurobiological Mechanisms for the Regulation of Mammalian Sleep-Wake Behavior: Reinterpretation of Historical Evidence and Inclusion of Contemporary Cellular and Molecular Evidence

PubMed Central

Datta, Subimal; MacLean, Robert Ross

2007-01-01

At its most basic level, the function of mammalian sleep can be described as a restorative process of the brain and body; recently, however, progressive research has revealed a host of vital functions to which sleep is essential. Although many excellent reviews on sleep behavior have been published, none have incorporated contemporary studies examining the molecular mechanisms that govern the various stages of sleep. Utilizing a holistic approach, this review is focused on the basic mechanisms involved in the transition from wakefulness, initiation of sleep and the subsequent generation of slow-wave sleep and rapid eye movement (REM) sleep. Additionally, using recent molecular studies and experimental evidence that provides a direct link to sleep as a behavior, we have developed a new model, the Cellular-Molecular-Network model, explaining the mechanisms responsible for regulating REM sleep. By analyzing the fundamental neurobiological mechanisms responsible for the generation and maintenance of sleep-wake behavior in mammals, we intend to provide a broader understanding of our present knowledge in the field of sleep research. PMID:17445891

Accelerated aging studies of UHMWPE. I. Effect of resin, processing, and radiation environment on resistance to mechanical degradation.

PubMed

Edidin, A A; Herr, M P; Villarraga, M L; Muth, J; Yau, S S; Kurtz, S M

2002-08-01

The resin and processing route have been identified as potential variables influencing the mechanical behavior, and hence the clinical performance, of ultra-high molecular weight polyethylene (UHMWPE) orthopedic components. Researchers have reported that components fabricated from 1900 resin may oxidize to a lesser extent than components fabricated from GUR resin during shelf aging after gamma sterilization in air. Conflicting reports on the oxidation resistance for 1900 raise the question of whether resin or manufacturing method, or an interaction between resin and manufacturing method, influences the mechanical behavior of UHMWPE. We conducted a series of accelerated aging studies (no aging, aging in oxygen or in nitrogen) to systematically examine the influence of resin (GUR or 1900), manufacturing method (bulk compression molding or extrusion), and sterilization method (none, in air, or in nitrogen) on the mechanical behavior of UHMWPE. The small punch testing technique was used to evaluate the mechanical behavior of the materials, and Fourier transform infrared spectroscopy was used to characterize the oxidation in selected samples. Our study showed that the sterilization environment, aging condition, and specimen location (surface or subsurface) significantly affected the mechanical behavior of UHMWPE. Each of the three polyethylenes evaluated seem to degrade according to a similar pathway after artificial aging in oxygen and gamma irradiation in air. The initial ability of the materials to exhibit post-yield strain hardening was significantly compromised by degradation. In general, there were only minor differences in the aging behavior of molded and extruded GUR 1050, whereas the molded 1900 material seemed to degrade slightly faster than either of the 1050 materials. Copyright 2002 Wiley Periodicals, Inc.

Constitutive behavior and progressive mechanical failure of electrodes in lithium-ion batteries

NASA Astrophysics Data System (ADS)

Zhang, Chao; Xu, Jun; Cao, Lei; Wu, Zenan; Santhanagopalan, Shriram

2017-07-01

The electrodes of lithium-ion batteries (LIB) are known to be brittle and to fail earlier than the separators during an external crush event. Thus, the understanding of mechanical failure mechanism for LIB electrodes (anode and cathode) is critical for the safety design of LIB cells. In this paper, we present experimental and numerical studies on the constitutive behavior and progression of failure in LIB electrodes. Mechanical tests were designed and conducted to evaluate the constitutive properties of porous electrodes. Constitutive models were developed to describe the stress-strain response of electrodes under uniaxial tensile and compressive loads. The failure criterion and a damage model were introduced to model their unique tensile and compressive failure behavior. The failure mechanism of LIB electrodes was studied using the blunt rod test on dry electrodes, and numerical models were built to simulate progressive failure. The different failure processes were examined and analyzed in detail numerically, and correlated with experimentally observed failure phenomena. The test results and models improve our understanding of failure behavior in LIB electrodes, and provide constructive insights on future development of physics-based safety design tools for battery structures under mechanical abuse.

Constitutive behavior and progressive mechanical failure of electrodes in lithium-ion batteries

DOE PAGES

Zhang, Chao; Xu, Jun; Cao, Lei; ...

2017-05-05

The electrodes of lithium-ion batteries (LIB) are known to be brittle and to fail earlier than the separators during an external crush event. Thus, the understanding of mechanical failure mechanism for LIB electrodes (anode and cathode) is critical for the safety design of LIB cells. In this paper, we present experimental and numerical studies on the constitutive behavior and progression of failure in LIB electrodes. Mechanical tests were designed and conducted to evaluate the constitutive properties of porous electrodes. Constitutive models were developed to describe the stress-strain response of electrodes under uniaxial tensile and compressive loads. The failure criterion andmore » a damage model were introduced to model their unique tensile and compressive failure behavior. The failure mechanism of LIB electrodes was studied using the blunt rod test on dry electrodes, and numerical models were built to simulate progressive failure. The different failure processes were examined and analyzed in detail numerically, and correlated with experimentally observed failure phenomena. Finally, the test results and models improve our understanding of failure behavior in LIB electrodes, and provide constructive insights on future development of physics-based safety design tools for battery structures under mechanical abuse.« less

Experimental study of thermo-mechanical behavior of a thermosetting shape-memory polymer

NASA Astrophysics Data System (ADS)

Liu, Ruoxuan; Li, Yunxin; Liu, Zishun

2018-01-01

The thermo-mechanical behavior of shape-memory polymers (SMPs) serves for the engineering applications of SMPs. Therefore the understanding of thermo-mechanical behavior of SMPs is of great importance. This paper investigates the influence of loading rate and loading level on the thermo-mechanical behavior of a thermosetting shape-memory polymer through experimental study. A series of cyclic tension tests and shape recovery tests at different loading conditions are performed to study the strain level and strain rate effect. The results of tension tests show that the thermosetting shape-memory polymer will behave as rubber material at temperature lower than the glass transition temperature (Tg) and it can obtain a large shape fix ratio at cyclic loading condition. The shape recovery tests exhibit that loading rate and loading level have little effect on the beginning and ending of shape recovery process of the thermosetting shape-memory polymer. Compared with the material which is deformed at temperature higher than Tg, the material deformed at temperature lower than Tg behaves a bigger recovery speed.

A Micromechanics Finite Element Model for Studying the Mechanical Behavior of Spray-On Foam Insulation (SOFI)

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Sullivan, Roy M.; Lerch, Bradley A.

2006-01-01

A micromechanics model has been constructed to study the mechanical behavior of spray-on foam insulation (SOFI) for the external tank. The model was constructed using finite elements representing the fundamental repeating unit of the SOFI microstructure. The details of the micromechanics model were based on cell observations and measured average cell dimensions discerned from photomicrographs. The unit cell model is an elongated Kelvin model (fourteen-sided polyhedron with 8 hexagonal and six quadrilateral faces), which will pack to a 100% density. The cell faces and cell edges are modeled using three-dimensional 20-node brick elements. Only one-eighth of the cell is modeled due to symmetry. By exercising the model and correlating the results with the macro-mechanical foam behavior obtained through material characterization testing, the intrinsic stiffness and Poisson s Ratio of the polymeric cell walls and edges are determined as a function of temperature. The model is then exercised to study the unique and complex temperature-dependent mechanical behavior as well as the fracture initiation and propagation at the microscopic unit cell level.

A Case Study of the De Novo Evolution of a Complex Odometric Behavior in Digital Organisms

PubMed Central

Grabowski, Laura M.; Bryson, David M.; Dyer, Fred C.; Pennock, Robert T.; Ofria, Charles

2013-01-01

Investigating the evolution of animal behavior is difficult. The fossil record leaves few clues that would allow us to recapitulate the path that evolution took to build a complex behavior, and the large population sizes and long time scales required prevent us from re-evolving such behaviors in a laboratory setting. We present results of a study in which digital organisms–self-replicating computer programs that are subject to mutations and selection–evolved in different environments that required information about past experience for fitness-enhancing behavioral decisions. One population evolved a mechanism for step-counting, a surprisingly complex odometric behavior that was only indirectly related to enhancing fitness. We examine in detail the operation of the evolved mechanism and the evolutionary transitions that produced this striking example of a complex behavior. PMID:23577113

Relationship between disease-specific structures of amyloid fibrils and their mechanical properties

NASA Astrophysics Data System (ADS)

Yoon, Gwonchan; Kab Kim, Young; Eom, Kilho; Na, Sungsoo

2013-01-01

It has recently been reported that the mechanical behavior of prion nanofibrils may play a critical role in expression of neurodegenerative diseases. In this work, we have studied the mechanical behavior of HET-s prion nanofibrils using an elastic network model. We have shown that the mechanical properties of prion nanofibrils formed as left-handed β-helices are different from those of non-prion nanofibrils formed as right-handed β-helices. In particular, the bending behavior of prion nanofibrils depends on the length of the nanofibril and that the bending rigidity of the prion nanofibril is larger than that of the non-prion nanofibril.

Evolution of the Deformation Behavior of Sn-Rich Solders during Cyclic Fatigue

NASA Astrophysics Data System (ADS)

Wentlent, Luke Arthur

Continuous developments in the electronics industry have provided a critical need for a quantitative, fundamental understanding of the behavior of SnAgCu (SAC) solders in both isothermal and thermal fatigue conditions. This study examines the damage behavior of Sn-based solders in a constant amplitude and variable amplitude environment. In addition, damage properties are correlated with crystal orientation and slip behavior. Select solder joints were continuously characterized and tested repeatedly in order to eliminate the joint to joint variation due to the anisotropy of beta-Sn. Characterization was partitioned into three different categories: effective properties and slip behavior, creep mechanisms and crystal morphology development, and atomic behavior and evolution. Active slip systems were correlated with measured properties. Characterization of the mechanical behavior was performed by the calculation and extrapolation of the elastic modulus, work, effective stiffness, Schmid factors, and time-dependent plasticity (creep). Electron microscopy based characterization methods included Scanning Electron Microscopy (SEM), Electron Backscattering Diffraction (EBSD), and Transmission Electron Microscopy (TEM). Testing showed a clear evolution of the steady-state creep mechanism when the cycling amplitudes were varied, from dislocation controlled to diffusion controlled creep. Dislocation behavior was examined and shown to evolve differently in single amplitude vs. variable amplitude testing. Finally, the mechanism of the recrystallization behavior of the beta-Sn was observed. This work fills a gap in the literature, providing a systematic study which identifies how the damage behavior in Sn-alloys depends upon the previous damage. A link is made between the observed creep behavior and the dislocation observations, providing a unified picture. Information developed in this work lays a stepping stone to future fundamental analyses as well as clarifying aspects of the mechanistic behavior of Sn and Sn-based alloys.

Comparative analysis of torsional and bending behavior through finite-element models of 5 Ni-Ti endodontic instruments.

PubMed

Arbab-Chirani, Reza; Chevalier, Valérie; Arbab-Chirani, Shabnam; Calloch, Sylvain

2011-01-01

The objectives of this study were to compare numerically the bending and torsional mechanical behavior of 5 endodontic rotary Ni-Ti instruments with equivalent size and various designs for tapers, pitch, and cutting blades.First, the geometries of Hero (20/0.06), HeroShaper (20/0.06), ProFile (20/0.06), Mtwo (20/0.06), and ProTaper F1 were generated by finite element code. Then, the 2 most representative clinical loadings, i.e., bending and torsion, were studied with an ad hoc model for the superelasticity of Ni-Ti. Bending was generated by tip deflection and torsion by a constant twist-angle of the tip. Mechanical behavior of these 5 endodontic rotary Ni-Ti instruments could be evaluated and compared. Protaper F1 presented the greatest level of bending stress and torque. Hero and HeroShaper were more rigid than ProFile and Mtwo. This numerical comparison evaluated the effects of the geometrical parameters on the instrumental mechanical behavior. The 5 endodontic instruments, investigated in the present study, do not have the same bending and torsional mechanical behavior. Each clinician must be aware of these behavior differences so as to use the adequate file according to the clinical situation and to the manufacturer's recommendations. Copyright © 2011 Mosby, Inc. All rights reserved.

On the Behavioral Side of Procrastination: Exploring Behavioral Delay in Real-Life Settings

PubMed Central

Svartdal, Frode; Granmo, Sjur; Færevaag, Fredrik S.

2018-01-01

This paper examines how procrastinators behave differently from non-procrastinators in implementing intended behavior. By focusing on time-related attributes of behavior, we demonstrate in five studies (aggregated N = 965) that onset delay seems to be a preferred option for procrastinators in common daily situations. Thus, when an action possibility is available for intended behavior, procrastinators tend to delay behavior onset, both in actual behavior and in onset preferences, often instigating chains of events with negative consequences. We discuss possible mechanisms responsible for such delays and explore how such mechanisms generate and sustain dilatory behavior. We conclude that a better understanding of why behavioral delays occur in early phases of action implementation is of importance in understanding and preventing procrastination. PMID:29867696

On the Behavioral Side of Procrastination: Exploring Behavioral Delay in Real-Life Settings.

PubMed

Svartdal, Frode; Granmo, Sjur; Færevaag, Fredrik S

2018-01-01

This paper examines how procrastinators behave differently from non-procrastinators in implementing intended behavior. By focusing on time-related attributes of behavior, we demonstrate in five studies (aggregated N = 965) that onset delay seems to be a preferred option for procrastinators in common daily situations. Thus, when an action possibility is available for intended behavior, procrastinators tend to delay behavior onset, both in actual behavior and in onset preferences, often instigating chains of events with negative consequences. We discuss possible mechanisms responsible for such delays and explore how such mechanisms generate and sustain dilatory behavior. We conclude that a better understanding of why behavioral delays occur in early phases of action implementation is of importance in understanding and preventing procrastination.

The effect of various metallurgical parameters on the flow and fracture behavior of polycrystalline NiAl near the brittle-to-ductile transition

NASA Technical Reports Server (NTRS)

Noebe, Ronald D.

1994-01-01

An investigation of the effect of various metallurgical parameters such as interfaces, allowing additions, test temperature, and strain rate on the flow and fracture behavior of polycrystalline NiAl is summarized. From this study, a more complete understanding of the deformation and fracture behavior of polycrystalline NiAl near the brittle-to-ductile transition temperature has been developed. A mechanism for the BDTT is proposed that is based on the operation of localized dislocation climb processes that operate within the vicinity of the grain boundaries and provide the additional deformation mechanisms necessary for grain-to-grain compatibility during plastic deformation. Finally, methods for improving the low temperature mechanical behavior of NiAl were considered and reviewed within the context of the present knowledge of NiAl-based materials and the operative deformation and fracture mechanisms determined in this study. Special emphasis was placed on the use of second phases for improving low temperature properties.

Understanding the Personality and Behavioral Mechanisms Defining Hypersexuality in Men Who Have Sex with Men

PubMed Central

Miner, Michael H.; Romine, Rebecca Swinburne; Raymond, Nancy; Janssen, Erick; MacDonald, Angus; Coleman, Eli

2016-01-01

Objective The purpose of this study was to investigate personality factors and behavioral mechanisms that are relevant to hypersexuality in men who have sex with men. Method A sample of 242 men who have sex with men were recruited from various sites in a moderate size mid-western city. Participants were assigned to hypersexuality or control group using a SCID-type interview. Self-report inventories were administered that measured the broad band personality constructs of positive emotionality, negative emotionality and constraint, and more narrow constructs related to sexual behavioral control, behavioral activation, behavioral inhibition, sexual excitation, sexual inhibition, impulsivity, ADHD, and sexual behavior. Hierarchical logistic regression was used to determine the relationship between these personality and behavioral variables and group membership. Results A hierarchical logistic regression, controlling for age, revealed a significant positive relationship between hypersexuality and negative emotionality and a negative relationship with constraint. None of the behavioral mechanism variables entered this equation. However, a hierarchical multiple regression predicting sexual behavioral control indicated that lack of such control was positively related to sexual excitation and sexual inhibition due to the threat of performance failure and negatively related to sexual inhibition due to the threat of performance consequences and general behavioral inhibition Conclusions Hypersexuality was found to be related to two broad personality factors that are characterized by emotional reactivity, risk-taking, and impulsivity. The associated lack of sexual behavior control is influenced by both sexual excitatory and inhibitory mechanisms, but not general behavioral activation and inhibitory mechanisms. PMID:27486137

A toolbox to explore the mechanics of living embryonic tissues

PubMed Central

Campàs, Otger

2016-01-01

The sculpting of embryonic tissues and organs into their functional morphologies involves the spatial and temporal regulation of mechanics at cell and tissue scales. Decades of in vitro work, complemented by some in vivo studies, have shown the relevance of mechanical cues in the control of cell behaviors that are central to developmental processes, but the lack of methodologies enabling precise, quantitative measurements of mechanical cues in vivo have hindered our understanding of the role of mechanics in embryonic development. Several methodologies are starting to enable quantitative studies of mechanics in vivo and in situ, opening new avenues to explore how mechanics contributes to shaping embryonic tissues and how it affects cell behavior within developing embryos. Here we review the present methodologies to study the role of mechanics in living embryonic tissues, considering their strengths and drawbacks as well as the conditions in which they are most suitable. PMID:27061360

A toolbox to explore the mechanics of living embryonic tissues.

PubMed

Campàs, Otger

2016-07-01

The sculpting of embryonic tissues and organs into their functional morphologies involves the spatial and temporal regulation of mechanics at cell and tissue scales. Decades of in vitro work, complemented by some in vivo studies, have shown the relevance of mechanical cues in the control of cell behaviors that are central to developmental processes, but the lack of methodologies enabling precise, quantitative measurements of mechanical cues in vivo have hindered our understanding of the role of mechanics in embryonic development. Several methodologies are starting to enable quantitative studies of mechanics in vivo and in situ, opening new avenues to explore how mechanics contributes to shaping embryonic tissues and how it affects cell behavior within developing embryos. Here we review the present methodologies to study the role of mechanics in living embryonic tissues, considering their strengths and drawbacks as well as the conditions in which they are most suitable. Copyright © 2016 Elsevier Ltd. All rights reserved.

Study on the Factors Affecting the Mechanical Behavior of Electron Beam Melted Ti6Al4V

NASA Astrophysics Data System (ADS)

Pirozzi, Carmine; Franchitti, Stefania; Borrelli, Rosario; Caiazzo, Fabrizia; Alfieri, Vittorio; Argenio, Paolo

2017-09-01

In this study, a mechanical characterization has been performed on EBM built Ti-6Al-4V tensile samples. The results of tensile tests have shown a different behavior between two sets of specimens: as built and machined ones. Supporting investigations have been carried out in order to physically explain the statistical difference of mechanical performances. Cylindrical samples which represent the tensile specimens geometry have been EBM manufactured and then investigated in their as built conditions from macrostructural and microstructural point of view. In order to make robust this study, cylindrical samples have been EBM manufactured with different size and at different height from build plate. The reason of this choice was arisen from the need of understanding if other factors as the massivity and specific location could affect the microstructure and defects generations consequently influencing the mechanical behavior of the EBMed components. The results of this study have proved that the irregularity of external circular surfaces of examined cylinders, reducing significantly the true cross section withstanding the applied load, has given a comprehensive physical explanation of the different tensile behavior of the two sets of tensile specimens.

Hypergravity-induced altered behavior in Drosophila

NASA Astrophysics Data System (ADS)

Hosamani, Ravikumar; Wan, Judy; Marcu, Oana; Bhattacharya, Sharmila

2012-07-01

Microgravity and mechanical stress are important factors of the spaceflight environment, and affect astronaut health and behavior. Structural, functional, and behavioral mechanisms of all cells and organisms are adapted to Earth's gravitational force, 1G, while altered gravity can pose challenges to their adaptability to this new environment. On ground, hypergravity paradigms have been used to predict and complement studies on microgravity. Even small changes that take place at a molecular and genetic level during altered gravity may result in changes in phenotypic behavior. Drosophila provides a robust and simple, yet very reliable model system to understand the complexity of hypergravity-induced altered behavior, due to availability of a plethora of genetic tools. Locomotor behavior is a sensitive parameter that reflects the array of molecular adaptive mechanisms recruited during exposure to altered gravity. Thus, understanding the genetic basis of this behavior in a hypergravity environment could potentially extend our understanding of mechanisms of adaptation in microgravity. In our laboratory we are trying to dissect out the cellular and molecular mechanisms underlying hypergravity-induced oxidative stress, and its potential consequences on behavioral alterations by using Drosophila as a model system. In the present study, we employed pan-neuronal and mushroom body specific knock-down adult flies by using Gal4/UAS system to express inverted repeat transgenes (RNAi) to monitor and quantify the hypergravity-induced behavior in Drosophila. We established that acute hypergravity (3G for 60 min) causes a significant and robust decrease in the locomotor behavior in adult Drosophila, and that this change is dependent on genes related to Parkinson's disease, such as DJ-1α , DJ-1β , and parkin. In addition, we also showed that anatomically the control of this behavior is significantly processed in the mushroom body region of the fly brain. This work links a molecular mechanism of response to changes in gravity with a phenotypical outcome. Characterizing the changes in altered gravity that are consequential for the overall physiology of organisms is crucial for assessing the risks of long-term space travel.

Mechanical Behavior and Fatigue Studies of Rubber Components Used in Tracked Vehicles

DTIC Science & Technology

2010-08-17

durability to this elastomers and polybutadiene is rubber , which gives rubber -like properties. SBR has good abrasion resistance and good aging ...SIMULATION, TESTING AND VALIDATION (MSTV) MINI-SYMPOSIUM AUGUST 17-19 DEARBORN, MICHIGAN MECHANICAL BEHAVIOR AND FATIGUE STUDIES OF RUBBER COMPONENTS USED...Analytics Group US Army TARDEC Warren, MI ABSTRACT In this study, a styrene butadiene rubber , which is similar to the rubber used in road wheel

[The development of antisocial behavior: psychobiological and environmental factors and gene-environment interactions].

PubMed

Gallardo-Pujol, D; Forero, C G; Maydeu-Olivares, A; Andrés-Pueyo, A

Antisocial behavior is a complex phenomenon with strong implications in neurology and psychiatry. In order to study the ontogenetic development of antisocial behavior, we must check for the existence of physiological mechanisms related to it, and to understand its environmentally-modulated functioning. To review the state-of-the-art of the development of antisocial behavior, and especially, of the interaction between environmental and genetic factors. Recent research has highlighted certain brain alterations linked to violent behavior, either at structural, or functional or biochemical levels. Genetic research has also made some advances in this field, discovering some genes--i.e. monoamineoxidase A (MAOA)--related to antisocial behavior. However, the importance of environmental factors in its development must not be left behind. Recent studies have shown that individuals carrying a low transcriptional activity allele of the MAOA gene, and that also suffered severe maltreatment are more prone to antisocial behavior. This interaction is biologically relevant, as there are underlying biological mechanisms that may be able to explain the ethiopathogeny of antisocial behavior. Although the works herein presented pioneered the field, they are limited by the fact that all the reviewed variables are associated to antisocial behavior, but they lack direct causal evidence of their effects on antisocial behavior. Undoubtedly, future research on psychobiological mechanisms and the understanding of their environmental modulation will help finding therapeutic targets and preventive strategies for antisocial behavior.

Sedentary behavior and sleep: paradoxical effects in association with childhood obesity.

PubMed

Must, A; Parisi, S M

2009-04-01

Sedentary behavior and sleep may be working in concert to increase the likelihood of a child becoming overweight, but in paradoxical ways. Reduction of sedentary behavior (that is, media screen time) has been extensively researched and touted as an intervention target. Inadequate sleep as a putative risk factor for obesity is only beginning to be explored. In this paper, we review the current state of research regarding these factors, and describe the existing evidence and mechanisms proposed to explain these relationships. Whereas the association between weight and sedentary behavior has been consistently shown in observational studies, effect sizes are small, and multiple mechanisms appear to be operating. Recent cross-sectional and longitudinal evidence suggests a link between short sleep duration and weight. Possible mechanisms here include direct metabolic effects as well as indirect behavioral pathways, including the presence of electronic media in children's bedrooms. Measurement issues present a challenge to both areas of research. Prospective studies that include more accurate measures of both sedentary behavior and of sleep will be needed to clarify causal pathways.

Numerical and Experimental Investigations on Mechanical Behavior of Composite Corrugated Core

NASA Astrophysics Data System (ADS)

Dayyani, Iman; Ziaei-Rad, Saeed; Salehi, Hamid

2012-06-01

Tensile and flexural characteristics of corrugated laminate panels were studied using numerical and analytical methods and compared with experimental data. Prepreg laminates of glass fiber plain woven cloth were hand-laid by use of a heat gun to ease the creation of the panel. The corrugated panels were then manufactured by using a trapezoidal machined aluminium mould. First, a series of simple tension tests were performed on standard samples to evaluate the material characteristics. Next, the corrugated panels were subjected to tensile and three-point bending tests. The force-displacement graphs were recorded. Numerical and analytical solutions were proposed to simulate the mechanical behavior of the panels. In order to model the energy dissipation due to delamination phenomenon observed in tensile tests in all members of corrugated core, plastic behavior was assigned to the whole geometry, not only to the corner regions. Contrary to the literature, it is shown that the three-stage mechanical behavior of composite corrugated core is not confined to aramid reinforced corrugated laminates and can be observed in other types such as fiber glass. The results reveal that the mechanical behavior of the core in tension is sensitive to the variation of core height. In addition, for the first time, the behavior of composite corrugated core was studied and verified in bending. Finally, the analytical and numerical results were validated by comparing them with experimental data. A good degree of correlation was observed which showed the suitability of the finite element model for predicting the mechanical behavior of corrugated laminate panels.

Dynamic mechanical control of local vacancies in NiO thin films

NASA Astrophysics Data System (ADS)

Seol, Daehee; Yang, Sang Mo; Jesse, Stephen; Choi, Minseok; Hwang, Inrok; Choi, Taekjib; Park, Bae Ho; Kalinin, Sergei V.; Kim, Yunseok

2018-07-01

The manipulation of local ionic behavior via external stimuli in oxide systems is of great interest because it can help in directly tuning material properties. Among external stimuli, mechanical force has attracted intriguing attention as novel stimulus for ionic modulation. Even though effectiveness of mechanical force on local ionic modulation has been validated in terms of static effect, its real-time i.e., dynamic, behavior under an application of the force is barely investigated in spite of its crucial impact on device performance such as force or pressure sensors. In this study, we explore dynamic ionic behavior modulated by mechanical force in NiO thin films using electrochemical strain microscopy (ESM). Ionically mediated ESM hysteresis loops were significantly varied under an application of mechanical force. Based on these results, we were able to investigate relative relationship between the force and voltage effects on ionic motion and, further, control effectively ionic behavior through combination of mechanical and electrical stimuli. Our results can provide comprehensive information on the effect of mechanical forces on ionic dynamics in ionic systems.

Dynamic mechanical control of local vacancies in NiO thin films.

PubMed

Seol, Daehee; Yang, Sang Mo; Jesse, Stephen; Choi, Minseok; Hwang, Inrok; Choi, Taekjib; Park, Bae Ho; Kalinin, Sergei V; Kim, Yunseok

2018-07-06

The manipulation of local ionic behavior via external stimuli in oxide systems is of great interest because it can help in directly tuning material properties. Among external stimuli, mechanical force has attracted intriguing attention as novel stimulus for ionic modulation. Even though effectiveness of mechanical force on local ionic modulation has been validated in terms of static effect, its real-time i.e., dynamic, behavior under an application of the force is barely investigated in spite of its crucial impact on device performance such as force or pressure sensors. In this study, we explore dynamic ionic behavior modulated by mechanical force in NiO thin films using electrochemical strain microscopy (ESM). Ionically mediated ESM hysteresis loops were significantly varied under an application of mechanical force. Based on these results, we were able to investigate relative relationship between the force and voltage effects on ionic motion and, further, control effectively ionic behavior through combination of mechanical and electrical stimuli. Our results can provide comprehensive information on the effect of mechanical forces on ionic dynamics in ionic systems.

Physical Activity for Cognitive and Mental Health in Youth: A Systematic Review of Mechanisms.

PubMed

Lubans, David; Richards, Justin; Hillman, Charles; Faulkner, Guy; Beauchamp, Mark; Nilsson, Michael; Kelly, Paul; Smith, Jordan; Raine, Lauren; Biddle, Stuart

2016-09-01

Physical activity can improve cognitive and mental health, but the underlying mechanisms have not been established. To present a conceptual model explaining the mechanisms for the effect of physical activity on cognitive and mental health in young people and to conduct a systematic review of the evidence. Six electronic databases (PubMed, PsycINFO, SCOPUS, Ovid Medline, SportDiscus, and Embase) were used. School-, home-, or community-based physical activity intervention or laboratory-based exercise interventions were assessed. Studies were eligible if they reported statistical analyses of changes in the following: (1) cognition or mental health; and (2) neurobiological, psychosocial, and behavioral mechanisms. Data relating to methods, assessment period, participant characteristics, intervention type, setting, and facilitator/delivery were extracted. Twenty-five articles reporting results from 22 studies were included. Mechanisms studied were neurobiological (6 studies), psychosocial (18 studies), and behavioral (2 studies). Significant changes in at least 1 potential neurobiological mechanism were reported in 5 studies, and significant effects for at least 1 cognitive outcome were also found in 5 studies. One of 2 studies reported a significant effect for self-regulation, but neither study reported a significant impact on mental health. Small number of studies and high levels of study heterogeneity. The strongest evidence was found for improvements in physical self-perceptions, which accompanied enhanced self-esteem in the majority of studies measuring these outcomes. Few studies examined neurobiological and behavioral mechanisms, and we were unable to draw conclusions regarding their role in enhancing cognitive and mental health. Copyright © 2016 by the American Academy of Pediatrics.

Structural versus dynamical origins of mean-field behavior in a self-organized critical model of neuronal avalanches

NASA Astrophysics Data System (ADS)

Moosavi, S. Amin; Montakhab, Afshin

2015-11-01

Critical dynamics of cortical neurons have been intensively studied over the past decade. Neuronal avalanches provide the main experimental as well as theoretical tools to consider criticality in such systems. Experimental studies show that critical neuronal avalanches show mean-field behavior. There are structural as well as recently proposed [Phys. Rev. E 89, 052139 (2014), 10.1103/PhysRevE.89.052139] dynamical mechanisms that can lead to mean-field behavior. In this work we consider a simple model of neuronal dynamics based on threshold self-organized critical models with synaptic noise. We investigate the role of high-average connectivity, random long-range connections, as well as synaptic noise in achieving mean-field behavior. We employ finite-size scaling in order to extract critical exponents with good accuracy. We conclude that relevant structural mechanisms responsible for mean-field behavior cannot be justified in realistic models of the cortex. However, strong dynamical noise, which can have realistic justifications, always leads to mean-field behavior regardless of the underlying structure. Our work provides a different (dynamical) origin than the conventionally accepted (structural) mechanisms for mean-field behavior in neuronal avalanches.

Food Intake and Eating Behavior After Bariatric Surgery.

PubMed

Al-Najim, Werd; Docherty, Neil G; le Roux, Carel W

2018-07-01

Obesity is an escalating global chronic disease. Bariatric surgery is a very efficacious treatment for obesity and its comorbidities. Alterations to gastrointestinal anatomy during bariatric surgery result in neurological and physiological changes affecting hypothalamic signaling, gut hormones, bile acids, and gut microbiota, which coalesce to exert a profound influence on eating behavior. A thorough understanding of the mechanisms underlying eating behavior is essential in the management of patients after bariatric surgery. Studies investigating candidate mechanisms have expanded dramatically in the last decade. Herein we review the proposed mechanisms governing changes in eating behavior, food intake, and body weight after bariatric surgery. Additive or synergistic effects of both conditioned and unconditioned factors likely account for the complete picture of changes in eating behavior. Considered application of strategies designed to support the underlying principles governing changes in eating behavior holds promise as a means of optimizing responses to surgery and long-term outcomes.

Mechanical and thermal behavior of ionic polymer metal composites: effects of electroded metals

NASA Astrophysics Data System (ADS)

Park, Il-Seok; Kim, Sang-Mun; Kim, Kwang J.

2007-08-01

In this study, we investigated the mechanical properties of various types of ionic polymer-metal composites (IPMCs) and Pt, Au, Pd, and Pt electroded ionic liquid (IL-Pt) IPMCs, by testing tensile modulus and dynamic mechanical behavior. The SEM was utilized to investigate the characteristics of the doped electroding layer, and the DSC was probed in order to look into the thermal behavior of various types of IPMCs. Au IPMCs, having a 5-7 µm-doped layer and nanosized Au particles (ca. 10 nm), showed the highest tensile strength (56 MPa) and modulus (602 MPa) in dried conditions. With regards to thermal behavior, Au IPMC had the highest Tg (153 °C) and Tm (263 °C) in both the DMA and DSC results. The fracture behavior of various types of IPMCs followed the behavior of the base material, Nafion™, which is represented as the semicrystalline polymer characteristic.

Mechanisms of deterioration of nutrients. [retention of flavor during freeze drying

NASA Technical Reports Server (NTRS)

Karel, M.; Flink, J. M.

1975-01-01

The retention of flavor during freeze drying was studied with model systems. Mechanisms by which flavor retention phenomena is explained were developed and process conditions specified so that flavor retention is optimized. The literature is reviewed and results of studies of the flavor retention behavior of a number of real food products, including both liquid and solid foods are evaluated. Process parameters predicted by the mechanisms to be of greatest significance are freezing rate, initial solids content, and conditions which result in maintenance of sample structure. Flavor quality for the real food showed the same behavior relative to process conditions as predicted by the mechanisms based on model system studies.

Socioeconomic Disparities in Health Behaviors

PubMed Central

Pampel, Fred C.; Krueger, Patrick M.; Denney, Justin T.

2011-01-01

The inverse relationships between socioeconomic status (SES) and unhealthy behaviors such as tobacco use, physical inactivity, and poor nutrition have been well demonstrated empirically but encompass diverse underlying causal mechanisms. These mechanisms have special theoretical importance because disparities in health behaviors, unlike disparities in many other components of health, involve something more than the ability to use income to purchase good health. Based on a review of broad literatures in sociology, economics, and public health, we classify explanations of higher smoking, lower exercise, poorer diet, and excess weight among low-SES persons into nine broad groups that specify related but conceptually distinct mechanisms. The lack of clear support for any one explanation suggests that the literature on SES disparities in health and health behaviors can do more to design studies that better test for the importance of the varied mechanisms. PMID:21909182

The role of sphingolipids in neuronal plasticity of the brain.

PubMed

Sonnino, Sandro; Prinetti, Alessandro

2016-05-01

This Editorial highlights a study by Müller et al. in which the authors suggest a new sphingolipid-dependent mechanism for behavioral extinction. Their study should be considered in the broad perspective of sphingolipid metabolic pathways and traffic (depicted in the graphic). Read the highlighted article 'A sphingolipid mechanism for behavioral extinction' on page 589. © 2016 International Society for Neurochemistry.

Engineering three-dimensional cell mechanical microenvironment with hydrogels.

PubMed

Huang, Guoyou; Wang, Lin; Wang, Shuqi; Han, Yulong; Wu, Jinhui; Zhang, Qiancheng; Xu, Feng; Lu, Tian Jian

2012-12-01

Cell mechanical microenvironment (CMM) significantly affects cell behaviors such as spreading, migration, proliferation and differentiation. However, most studies on cell response to mechanical stimulation are based on two-dimensional (2D) planar substrates, which cannot mimic native three-dimensional (3D) CMM. Accumulating evidence has shown that there is a significant difference in cell behavior in 2D and 3D microenvironments. Among the materials used for engineering 3D CMM, hydrogels have gained increasing attention due to their tunable properties (e.g. chemical and mechanical properties). In this paper, we provide an overview of recent advances in engineering hydrogel-based 3D CMM. Effects of mechanical cues (e.g. hydrogel stiffness and externally induced stress/strain in hydrogels) on cell behaviors are described. A variety of approaches to load mechanical stimuli in 3D hydrogel-based constructs are also discussed.

Loss of Ahi1 Impairs Neurotransmitter Release and Causes Depressive Behaviors in Mice

PubMed Central

Zhai, Lijing; Sun, Miao; Miao, Zhigang; Li, Jizhen; Xu, Xingshun

2014-01-01

Major depression is becoming one of the most prevalent forms of psychiatric disorders. However, the mechanisms of major depression are still not well-understood. Most antidepressants are only effective in some patients and produce some serious side effects. Animal models of depression are therefore essential to unravel the mechanisms of depression and to develop novel therapeutic strategies. Our previous studies showed that Abelson helper integration site-1 (Ahi1) deficiency causes depression-like behaviors in mice. In this study, we characterized the biochemical and behavioral changes in Ahi1 knockout (KO) mice. In Ahi1 KO mice, neurotransmitters including serotonin and dopamine were significantly decreased in different brain regions. However, glutamate and GABA levels were not affected by Ahi1 deficiency. The antidepressant imipramine attenuated depressive behaviors and partially restored brain serotonin level in Ahi1 KO mice. Our findings suggest that Ahi1 KO mice can be used for studying the mechanisms of depression and screening therapeutic targets. PMID:24691070

Child abuse and the balance of power in parental relationships: an evolved domain-independent mental mechanism that accounts for behavioral variation.

PubMed

Handwerker, W P

2001-01-01

Previous studies use zero-order analyses to show a link between child abuse and exposure to "stepfathers." These studies rest on a proposed evolved, domain-specific cognitive mechanism that induces adult males to abuse or kill offspring not their own and, so, contribute directly to reproductive success. However, child abuse may reflect an evolved neurological mechanism that creates behavioral plasticity and adaptability by assigning emotional weights (which in consciousness appear rationalized as costs and benefits) to choice alternatives in all behavioral domains. This mechanism should act as a selective mechanism to create enhanced ability to avoid predation (social exploitation) and to obtain access to resources, given the properties of specific ecosystems, and should control behavioral responses to variation in the balance of power in social relationships. Power equalities should elicit good treatment for both parties; power inequalities, by contrast, should elicit exploitative and coercive behavior on the part of those who hold the balance of power. This paper reports a test of both hypotheses simultaneously, controlling for a standard social science risk factor (growing up in poverty). Once we control for the balance of power in parental relationships, exposure to a stepfather and growing up in poverty show no effect on the intensity of child abuse. Powerful women negotiated affectionate behavior from their partners for both themselves and their children; powerless women's negotiations with partners usually left both themselves and their children open to violence.

Heat treatment effect on the mechanical properties of industrial drawn copper wires

NASA Astrophysics Data System (ADS)

Beribeche, Abdellatif; Boumerzoug, Zakaria; Ji, Vincent

2013-12-01

In this present investigation, the mechanical properties of industrial drawn copper wires have been studied by tensile tests. The effect of prior heat treatments at 500°C on the drawn wires behavior was the main goal of this investigation. We have found that the mechanical behavior of drawn wires depends strongly on those treatments. SEM observations of the wire cross section after tensile tests have shown that the mechanism of rupture was mainly controlled by the void formation.

Aggressive versus Nonaggressive Antisocial Behavior: Distinctive Etiological Moderation by Age

ERIC Educational Resources Information Center

Burt, S. Alexandra; Neiderhiser, Jenae M.

2009-01-01

Research has supported the existence of distinct behavioral patterns, demographic correlates, and etiologic mechanisms for aggressive (AGG) versus nonaggressive but delinquent (DEL) antisocial behavior. Though behavioral genetic studies have the potential to further crystallize these dimensions, inconsistent results have limited their…

Coupling of Mechanical Behavior of Lithium Ion Cells to Electrochemical-Thermal (ECT) Models for Battery Crush

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Chao; Santhanagopalan, Shriram; Pesaran, Ahmad

Vehicle crashes can lead to crushing of the battery, damaging lithium ion battery cells and causing local shorts, heat generation, and thermal runaway. Simulating all the physics and geometries at the same time is challenging and takes a lot of effort; thus, simplifications are needed. We developed a material model for simultaneously modeling the mechanical-electrochemical-thermal behavior, which predicted the electrical short, voltage drop, and thermal runaway behaviors followed by a mechanical abuse-induced short. The effect of short resistance on the battery cell performance was studied.

Dynamic Behavior and Optimization of Advanced Armor Ceramics: January-December 2011 Annual Report

DTIC Science & Technology

2015-03-01

however, under conventional methods of processing. To develop plasticity in ceramic like SiC, new fracture mechanisms and interesting behaviors need...and new fracture mechanisms . These improvements, in turn, could offer the potential for improved ballistic performance. Co-precipitation has been...experiments, the following deformed fragments were recovered for extensive SEM and TEM study.  A fracture mechanism map has been constructed in

Mechanical behavior and shape optimization of lining structure for subsea tunnel excavated in weathered slot

NASA Astrophysics Data System (ADS)

Li, Peng-fei; Zhou, Xiao-jun

2015-12-01

Subsea tunnel lining structures should be designed to sustain the loads transmitted from surrounding ground and groundwater during excavation. Extremely high pore-water pressure reduces the effective strength of the country rock that surrounds a tunnel, thereby lowering the arching effect and stratum stability of the structure. In this paper, the mechanical behavior and shape optimization of the lining structure for the Xiang'an tunnel excavated in weathered slots are examined. Eight cross sections with different geometric parameters are adopted to study the mechanical behavior and shape optimization of the lining structure. The hyperstatic reaction method is used through finite element analysis software ANSYS. The mechanical behavior of the lining structure is evidently affected by the geometric parameters of crosssectional shape. The minimum safety factor of the lining structure elements is set to be the objective function. The efficient tunnel shape to maximize the minimum safety factor is identified. The minimum safety factor increases significantly after optimization. The optimized cross section significantly improves the mechanical characteristics of the lining structure and effectively reduces its deformation. Force analyses of optimization process and program are conducted parametrically so that the method can be applied to the optimization design of other similar structures. The results obtained from this study enhance our understanding of the mechanical behavior of the lining structure for subsea tunnels. These results are also beneficial to the optimal design of lining structures in general.

Nanoscale size effects on the mechanical properties of platinum thin films and cross-sectional grain morphology

NASA Astrophysics Data System (ADS)

Abbas, K.; Alaie, S.; Ghasemi Baboly, M.; Elahi, M. M. M.; Anjum, D. H.; Chaieb, S.; Leseman, Z. C.

2016-01-01

The mechanical behavior of polycrystalline Pt thin films is reported for thicknesses of 75 nm, 100 nm, 250 nm, and 400 nm. These thicknesses correspond to transitions between nanocrystalline grain morphology types as found in TEM studies. Thinner samples display a brittle behavior, but as thickness increases the grain morphology evolves, leading to a ductile behavior. During evolution of the morphology, dramatic differences in elastic moduli (105-160 GPa) and strengths (560-1700 MPa) are recorded and explained by the variable morphology. This work suggests that in addition to the in-plane grain size of thin films, the transitions in cross-sectional morphologies of the Pt films significantly affect their mechanical behavior.

Mechanical Kinesiology.

ERIC Educational Resources Information Center

Barham, Jerry N.

Mechanical kinesiology is defined as a study of the mechanical factors affecting human movement, i.e., applying the physical laws of mechanics to the study of human motor behavior. This textbook on the subject is divided into thirty lessons. Each lesson is organized into three parts: a part on the text proper; a part entitled "study…

Neurobiological mechanisms of exercise and psychotherapy in depression: The SPeED study-Rationale, design, and methodological issues.

PubMed

Heinzel, Stephan; Rapp, Michael A; Fydrich, Thomas; Ströhle, Andreas; Terán, Christina; Kallies, Gunnar; Schwefel, Melanie; Heissel, Andreas

2018-02-01

Even though cognitive behavioral therapy has become a relatively effective treatment for major depressive disorder and cognitive behavioral therapy-related changes of dysfunctional neural activations were shown in recent studies, remission rates still remain at an insufficient level. Therefore, the implementation of effective augmentation strategies is needed. In recent meta-analyses, exercise therapy (especially endurance exercise) was reported to be an effective intervention in major depressive disorder. Despite these findings, underlying mechanisms of the antidepressant effect of exercise especially in combination with cognitive behavioral therapy have rarely been studied to date and an investigation of its neural underpinnings is lacking. A better understanding of the psychological and neural mechanisms of exercise and cognitive behavioral therapy would be important for developing optimal treatment strategies in depression. The SPeED study (Sport/Exercise Therapy and Psychotherapy-evaluating treatment Effects in Depressive patients) is a randomized controlled trial to investigate underlying physiological, neurobiological, and psychological mechanisms of the augmentation of cognitive behavioral therapy with endurance exercise. It is investigated if a preceding endurance exercise program will enhance the effect of a subsequent cognitive behavioral therapy. This study will include 105 patients diagnosed with a mild or moderate depressive episode according to the Diagnostic and Statistical Manual of Mental Disorders (4th ed.). The participants are randomized into one of three groups: a high-intensive or a low-intensive endurance exercise group or a waiting list control group. After the exercise program/waiting period, all patients receive an outpatient cognitive behavioral therapy treatment according to a standardized therapy manual. At four measurement points, major depressive disorder symptoms (Beck Depression Inventory, Hamilton Rating Scale for Depression), (neuro)biological measures (neural activations during working memory, monetary incentive delay task, and emotion regulation, as well as cortisol levels and brain-derived neurotrophic factor), neuropsychological test performance, and questionnaires (psychological needs, self-efficacy, and quality of life) are assessed. In this article, we report the design of the SPeED study and refer to important methodological issues such as including both high- and low-intensity endurance exercise groups to allow the investigation of dose-response effects and physiological components of the therapy effects. The main aims of this research project are to study effects of endurance exercise and cognitive behavioral therapy on depressive symptoms and to investigate underlying physiological and neurobiological mechanisms of these effects. Results may provide important implications for the development of effective treatment strategies in major depressive disorder, specifically concerning the augmentation of cognitive behavioral therapy by endurance exercise.

Separable Roles for Attentional Control Sub-Systems in Reading Tasks: A Combined Behavioral and fMRI Study

PubMed Central

Ihnen, S.K.Z.; Petersen, Steven E.; Schlaggar, Bradley L.

2015-01-01

Attentional control is important both for learning to read and for performing difficult reading tasks. A previous study invoked 2 mechanisms to explain reaction time (RT) differences between reading tasks with variable attentional demands. The present study combined behavioral and neuroimaging measures to test the hypotheses that there are 2 mechanisms of interaction between attentional control and reading; that these mechanisms are dissociable both behaviorally and neuro-anatomically; and that the 2 mechanisms involve functionally separable control systems. First, RT evidence was found in support of the 2-mechanism model, corroborating the previous study. Next, 2 sets of brain regions were identified as showing functional magnetic resonance imaging blood oxygen level-dependent activity that maps onto the 2-mechanism distinction. One set included bilateral Cingulo-opercular regions and mostly right-lateralized Dorsal Attention regions (CO/DA+). This CO/DA+ region set showed response properties consistent with a role in reporting which processing pathway (phonological or lexical) was biased for a particular trial. A second set was composed primarily of left-lateralized Frontal-parietal (FP) regions. Its signal properties were consistent with a role in response checking. These results demonstrate how the subcomponents of attentional control interact with subcomponents of reading processes in healthy young adults. PMID:24275830

Mechanical Properties of Additively Manufactured Thick Honeycombs.

PubMed

Hedayati, Reza; Sadighi, Mojtaba; Mohammadi Aghdam, Mohammad; Zadpoor, Amir Abbas

2016-07-23

Honeycombs resemble the structure of a number of natural and biological materials such as cancellous bone, wood, and cork. Thick honeycomb could be also used for energy absorption applications. Moreover, studying the mechanical behavior of honeycombs under in-plane loading could help understanding the mechanical behavior of more complex 3D tessellated structures such as porous biomaterials. In this paper, we study the mechanical behavior of thick honeycombs made using additive manufacturing techniques that allow for fabrication of honeycombs with arbitrary and precisely controlled thickness. Thick honeycombs with different wall thicknesses were produced from polylactic acid (PLA) using fused deposition modelling, i.e., an additive manufacturing technique. The samples were mechanically tested in-plane under compression to determine their mechanical properties. We also obtained exact analytical solutions for the stiffness matrix of thick hexagonal honeycombs using both Euler-Bernoulli and Timoshenko beam theories. The stiffness matrix was then used to derive analytical relationships that describe the elastic modulus, yield stress, and Poisson's ratio of thick honeycombs. Finite element models were also built for computational analysis of the mechanical behavior of thick honeycombs under compression. The mechanical properties obtained using our analytical relationships were compared with experimental observations and computational results as well as with analytical solutions available in the literature. It was found that the analytical solutions presented here are in good agreement with experimental and computational results even for very thick honeycombs, whereas the analytical solutions available in the literature show a large deviation from experimental observation, computational results, and our analytical solutions.

Effect of Heat Treatment Process on Microstructure and Fatigue Behavior of a Nickel-Base Superalloy

PubMed Central

Zhang, Peng; Zhu, Qiang; Chen, Gang; Qin, Heyong; Wang, Chuanjie

2015-01-01

The study of fatigue behaviors for nickel-base superalloys is very significant because fatigue damage results in serious consequences. In this paper, two kinds of heat treatment procedures (Pro.I and Pro.II) were taken to investigate the effect of heat treatment on microstructures and fatigue behaviors of a nickel-base superalloy. Fatigue behaviors were studied through total strain controlled mode at 650 °C. Manson-Coffin relationship and three-parameter power function were used to predict fatigue life. A good link between the cyclic/fatigue behavior and microscopic studies was established. The cyclic deformation mechanism and fatigue mechanism were discussed. The results show that the fatigue resistance significantly drops with the increase of total strain amplitudes. Manson-Coffin relationship can well predict the fatigue life for total strain amplitude from 0.5% to 0.8%. The fatigue resistance is related with heat treatment procedures. The fatigue resistance performance of Pro.I is better than that of Pro.II. The cyclic stress response behaviors are closely related to the changes of the strain amplitudes. The peak stress of the alloy gradually increases with the increase of total strain amplitudes. The main fracture mechanism is inhomogeneous deformation and the different interactions between dislocations and γ′ precipitates. PMID:28793559

Have studies of the developmental regulation of behavioral phenotypes revealed the mechanisms of gene-environment interactions?

PubMed Central

Hall, F. Scott; Perona, Maria T. G.

2012-01-01

This review addresses the recent convergence of our long-standing knowledge of the regulation of behavioral phenotypes by developmental experience with recent advances in our understanding of mechanisms regulating gene expression. This review supports a particular perspective on the developmental regulation of behavioral phenotypes: That the role of common developmental experiences (e.g. maternal interactions, peer interactions, exposure to a complex environment, etc.) is to fit individuals to the circumstances of their lives within bounds determined by long-standing (evolutionary) mechanisms that have shaped responses to critical and fundamental types of experience via those aspects of gene structure that regulate gene expression. The phenotype of a given species is not absolute for a given genotype but rather variable within bounds that are determined by mechanisms regulated by experience (e.g. epigenetic mechanisms). This phenotypic variation is not necessarily random, or evenly distributed along a continuum of description or measurement, but often highly disjointed, producing distinct, even opposing, phenotypes. The potentiality for these varying phenotypes is itself the product of evolution, the potential for alternative phenotypes itself conveying evolutionary advantage. Examples of such phenotypic variation, resulting from environmental or experiential influences, have a long history of study in neurobiology, and a number of these will be discussed in this review: neurodevelopmental experiences that produce phenotypic variation in visual perception, cognitive function, and emotional behavior. Although other examples will be discussed, particular emphasis will be made on the role of social behavior on neurodevelopment and phenotypic determination. It will be argued that an important purpose of some aspects of social behavior is regulation of neurobehavioral phenotypes by experience via genetic regulatory mechanisms. PMID:22643448

Direct Associations or Internal Transformations? Exploring the Mechanisms Underlying Sequential Learning Behavior

PubMed Central

Gureckis, Todd M.; Love, Bradley C.

2009-01-01

We evaluate two broad classes of cognitive mechanisms that might support the learning of sequential patterns. According to the first, learning is based on the gradual accumulation of direct associations between events based on simple conditioning principles. The other view describes learning as the process of inducing the transformational structure that defines the material. Each of these learning mechanisms predict differences in the rate of acquisition for differently organized sequences. Across a set of empirical studies, we compare the predictions of each class of model with the behavior of human subjects. We find that learning mechanisms based on transformations of an internal state, such as recurrent network architectures (e.g., Elman, 1990), have difficulty accounting for the pattern of human results relative to a simpler (but more limited) learning mechanism based on learning direct associations. Our results suggest new constraints on the cognitive mechanisms supporting sequential learning behavior. PMID:20396653

Mechanical stability of heat-treated nanoporous anodic alumina subjected to repetitive mechanical deformation

NASA Astrophysics Data System (ADS)

Bankova, A.; Videkov, V.; Tzaneva, B.; Mitov, M.

2018-03-01

We report studies on the mechanical response and deformation behavior of heat-treated nanoporous anodic alumina using a micro-balance test and experimental test equipment especially designed for this purpose. AAO samples were characterized mechanically by a three-point bending test using a micro-analytical balance. The deformation behavior was studied by repetitive mechanical bending of the AAO membranes using an electronically controlled system. The nanoporous AAO structures were prepared electrochemically from Al sheet substrates using a two-step anodizing technique in oxalic acid followed by heat treatment at 700 °C in air. The morphological study of the aluminum oxide layer after the mechanical tests and mechanical deformation was conducted using scanning electron and optical microscopy, respectively. The experimental results showed that the techniques proposed are simple and accurate; they could, therefore, be combined to constitute a method for mechanical stability assessment of nanostructured AAO films, which are important structural components in the design of MEMS devices and sensors.

Impact of mechanical stretch on the cell behaviors of bone and surrounding tissues

PubMed Central

Yu, Hye-Sun; Kim, Jung-Ju; Kim, Hae-Won; Lewis, Mark P; Wall, Ivan

2016-01-01

Mechanical loading is recognized to play an important role in regulating the behaviors of cells in bone and surrounding tissues in vivo. Many in vitro studies have been conducted to determine the effects of mechanical loading on individual cell types of the tissues. In this review, we focus specifically on the use of the Flexercell system as a tool for studying cellular responses to mechanical stretch. We assess the literature describing the impact of mechanical stretch on different cell types from bone, muscle, tendon, ligament, and cartilage, describing individual cell phenotype responses. In addition, we review evidence regarding the mechanotransduction pathways that are activated to potentiate these phenotype responses in different cell populations. PMID:26977284

What baboons can (not) tell us about natural language grammars.

PubMed

Poletiek, Fenna H; Fitz, Hartmut; Bocanegra, Bruno R

2016-06-01

Rey et al. (2012) present data from a study with baboons that they interpret in support of the idea that center-embedded structures in human language have their origin in low level memory mechanisms and associative learning. Critically, the authors claim that the baboons showed a behavioral preference that is consistent with center-embedded sequences over other types of sequences. We argue that the baboons' response patterns suggest that two mechanisms are involved: first, they can be trained to associate a particular response with a particular stimulus, and, second, when faced with two conditioned stimuli in a row, they respond to the most recent one first, copying behavior they had been rewarded for during training. Although Rey et al. (2012) 'experiment shows that the baboons' behavior is driven by low level mechanisms, it is not clear how the animal behavior reported, bears on the phenomenon of Center Embedded structures in human syntax. Hence, (1) natural language syntax may indeed have been shaped by low level mechanisms, and (2) the baboons' behavior is driven by low level stimulus response learning, as Rey et al. propose. But is the second evidence for the first? We will discuss in what ways this study can and cannot give evidential value for explaining the origin of Center Embedded recursion in human grammar. More generally, their study provokes an interesting reflection on the use of animal studies in order to understand features of the human linguistic system. Copyright © 2015 Elsevier B.V. All rights reserved.

Experimental Investigation of the Mechanical Behavior of a Filled Elastomer at Pressures Below 10 to the -6th Power Torr. Ph.D. Thesis - Va. Polytechnic Inst.

NASA Technical Reports Server (NTRS)

Gregory, G. L.

1972-01-01

The mechanical behavior of a filled elastomer was studied with emphasis on understanding the vacuum-material interactions occurring, and to develop analytical techniques for predicting the vacuum behavior. The test results indicate that two separate mechanisms are involved in the observed property changes: the first controls the time response to applied stress; the second determines the initial internal state of the materials as the result of stresses. It is concluded that the mechanical property changes are attributable to changes in the relaxation processes occurring in the material. These changes are brought about by outgassing of water. Recommendations for future investigations are included.

Associations Between Long-Term Gang Membership and Informal Social Control Processes, Drug Use, and Delinquent Behavior Among Mexican American Youth

PubMed Central

Cepeda, Alice; Saint Onge, Jarron M.; Nowotny, Kathryn M.; Valdez, Avelardo

2018-01-01

Research has found that among juveniles weak ties to informal social control entities such as parents, school, and conventional peers increase the probability of the initiation and continuation of deviant behaviors such as drug use and crime. Given the weak ties of formal social control mechanisms in highly disadvantaged communities, informal social control mechanisms are often an important deterrent that reduce or moderate engagement in deviant behaviors among serious and persistent offenders. This analysis examines the association between long-term gang membership and adolescent informal social control processes, drug use, and delinquency. This research is based on data from a study of 160 Mexican American male gang members between the ages of 16 and 20. Findings suggest that among gang members in this context, commonly studied informal control mechanisms such as the family and schools do not function to deter long-term gang membership that is associated with serious criminal and violent behavior and drug use. The implications for future research on desistance or continuation of antisocial behavior across the life course are discussed. PMID:25979430

Comparison of mechanical behavior between implant-simulated bone tissue and implant-jaw bone tissue interfaces based on Pull Out testing

NASA Astrophysics Data System (ADS)

Lopez, C.; Muñoz, J. C.; Pinillos, J. C.

2013-11-01

The main purpose of this research was to achieve a better understanding of the relationship within the mechanical properties of human cadaver jaw bone with kind D2 density regarding a substitute polymer to simulate bone tissue, proposed by the ASTM, to evaluate orthopedic implants. However, despite the existence of several densities of foams and his mechanical characterization has been classified into different degrees of tissue densities to simulate cancellous and cortical bone, the value of the densities are different contrasted with the densities of bone tissue, making difficult to establish direct relationship about mechanical behavior between the polymer and the bone material, and therefore no clear criteria known for choosing the polymeric foam which describes the mechanical behavior of tissue for a specific or particular study. To understand such behavior from bone tissue regarding the polymer samples, on this research was a dental implant inserted into the samples, and subjected to destructive Pull Out test according to ASTM F543The Pull Out strength was compared between implant-jawbone and implant-rigid polyurethane foam interfaces. Thus, the test pieces with mechanical behavior similar to bone tissue, enabling an approximation to choose degree appropriate of polymer to replace the bone tissue in future trials biomechanical.

Processing and Characterization of Cellulose Nanocrystals/Polylactic Acid Nanocomposite Films

PubMed Central

Sullivan, Erin M.; Moon, Robert J.; Kalaitzidou, Kyriaki

2015-01-01

The focus of this study is to examine the effect of cellulose nanocrystals (CNC) on the properties of polylactic acid (PLA) films. The films are fabricated via melt compounding and melt fiber spinning followed by compression molding. Film fracture morphology, thermal properties, crystallization behavior, thermo-mechanical behavior, and mechanical behavior were determined as a function of CNC content using scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, dynamic mechanical analysis, and tensile testing. Film crystallinity increases with increasing CNC content indicating CNC act as nucleating agents, promoting crystallization. Furthermore, the addition of CNC increased the film storage modulus and slightly broadened the glass transition region. PMID:28793701

Monogenic Mouse Models of Autism Spectrum Disorders: Common Mechanisms and Missing Links

PubMed Central

Hulbert, Samuel W.; Jiang, Yong-hui

2016-01-01

Autism Spectrum Disorders (ASDs) present unique challenges in the fields of genetics and neurobiology because of the clinical and molecular heterogeneity underlying these disorders. Genetic mutations found in ASD patients provide opportunities to dissect the molecular and circuit mechanisms underlying autistic behaviors using animal models. Ongoing studies of genetically modified models have offered critical insight into possible common mechanisms arising from different mutations, but links between molecular abnormalities and behavioral phenotypes remain elusive. The challenges encountered in modeling autism in mice demand a new analytic paradigm that integrates behavioral analysis with circuit-level analysis in genetically modified models with strong construct validity. PMID:26733386

Characterization of fatigue behavior of 2-D woven fabric reinforced ceramic matrix composite at elevated temperature. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Groner, D.J.

This study investigated the fatigue behavior and associated damage mechanisms in notched and unnotched enhanced SiC/SiC ceramic matrix composite specimens at 1100 deg C. Stiffness degradation, strain variation, and hysteresis were evaluated to characterize material behavior. Microscopic examination was performed to characterize damage mechanisms. During high cycle/low stress fatigue tests, far less fiber/matrix interface debond was evident than in low cycle/high stress fatigue tests. Notched specimens exhibited minimal stress concentration during monotonic tensile testing and minimal notch sensitivity during fatigue testing. Damage mechanisms were also similar to unnotched.

Genetic and epigenetic regulatory mechanisms of the oxytocin receptor gene (OXTR) and the (clinical) implications for social behavior.

PubMed

Tops, Sanne; Habel, Ute; Radke, Sina

2018-03-12

Oxytocin and the oxytocin receptor (OXTR) play an important role in a large variety of social behaviors. The oxytocinergic system interacts with environmental cues and is highly dependent on interindividual factors. Deficits in this system have been linked to mental disorders associated with social impairments, such as autism spectrum disorder (ASD). This review focuses on the modulation of social behavior by alterations in two domains of the oxytocinergic system. We discuss genetic and epigenetic regulatory mechanisms and alterations in these mechanisms that were found to have clinical implications for ASD. We propose possible explanations how these alterations affect the biological pathways underlying the aberrant social behavior and point out avenues for future research. We advocate the need for integration studies that combine multiple measures covering a broad range of social behaviors and link these to genetic and epigenetic profiles. Copyright © 2018. Published by Elsevier Inc.

The mechanical properties of ionic polymer-metal composites

NASA Astrophysics Data System (ADS)

Park, Il-Seok; Kim, Sang-Mun; Kim, Doyeon; Kim, Kwang J.

2007-04-01

In this study, we investigated the mechanical properties of various type ionic polymer-metal composites (IPMCs) and Pt, Au, Pd, and Pt electroded ionic liquid (IL-Pt) IPMCs, by testing tensile modulus and dynamic mechanical behavior. The SEM was utilized to investigate the characteristics of the doped electroding layer, and the DSC was probed in order to look into the thermal behavior of various types of IPMCs. Au IPMCs, having a 5~7 μm doped layer and nano-sized Au particles (ca. 10 nm), showed the highest tensile strength (56 MPa) and modulus (602 MPa) in a dried condition. In a thermal behavior, Au IPMC has the highest T g (153°C) and T m (263°C) in both the DMA and DSC results. The fracture behavior of various types IPMCs followed base material's behavior, Nafion TM, which is represented as the semicrystalline polymer characteristic.

Preparation, Electromechanical, and Structural Study of Carbon Nanotube/Gelatin Nanocomposites

DTIC Science & Technology

2008-01-15

surfactant sodium dodecyl sulfate (SDS). The swelling behavior and the bending mechanism of the composite and pure gelatin films were studied in order...vacuum-dried gels samples into a 0.1 M NaCl aqueous solution at room temperature. The incorporation of MWNT gradually decreased the swelling of the...ultrasonication in an aqueous medium with anionic surfactant sodium dodecyl sulfate (SDS). The swelling behavior and the bending mechanism of the

Novel paradigms to measure variability of behavior in early childhood: posture, gaze, and pupil dilation

PubMed Central

Hepach, Robert; Vaish, Amrisha; Tomasello, Michael

2015-01-01

A central challenge of investigating the underlying mechanisms of and the individual differences in young children’s behavior is the measurement of the internal physiological mechanism and the involved expressive emotions. Here, we illustrate two paradigms that assess concurrent indicators of both children’s social perception as well as their emotional expression. In one set of studies, children view situations while their eye movements are mapped onto a live scene. In these studies, children’s internal arousal is measured via changes in their pupil dilation by using eye tracking technology. In another set of studies, we measured children’s emotional expression via changes in their upper-body posture by using depth sensor imaging technology. Together, these paradigms can provide new insights into the internal mechanism and outward emotional expression involved in young children’s behavior. PMID:26217246

Making Decisions with the Future in Mind: Developmental and Comparative Identification of Mental Time Travel

ERIC Educational Resources Information Center

Suddendorf, T.; Busby, J.

2005-01-01

Mechanisms that produce behavior which increase future survival chances provide an adaptive advantage. The flexibility of human behavior is at least partly the result of one such mechanism, our ability to travel mentally in time and entertain potential future scenarios. We can study mental time travel in children using language. Current results…

Fuel treatment longevity in a Sierra Nevada mixed conifer forest

Treesearch

Scott. L. Stephens; Brandon M. Collins; Gary. Roller

2012-01-01

Understanding the longevity of fuel treatments in terms of their ability to maintain fire behavior and effects within a desired range is an important question. The objective of this study was to determine how fuels, forest structure, and predicted fire behavior changed 7-years after initial treatments. Three different treatments: mechanical only, mechanical plus fire,...

The Utility of Behavioral Economics in Expanding the Free-Feed Model of Obesity

PubMed Central

Rasmussen, Erin B.; Robertson, Stephen H.; Rodriguez, Luis R.

2016-01-01

Animal models of obesity are numerous and diverse in terms of identifying specific neural and peripheral mechanisms related to obesity; however, they are limited when it comes to behavior. The standard behavioral measure of food intake in most animal models occurs in a free-feeding environment. While easy and cost-effective for the researcher, the free-feeding environment omits some of the most important features of obesity-related food consumption—namely, properties of food availability, such as effort and delay to obtaining food. Behavior economics expands behavioral measures of obesity animal models by identifying such behavioral mechanisms. First, economic demand analysis allows researchers to understand the role of effort in food procurement, and how physiological and neural mechanisms are related. Second, studies on delay discounting contribute to a growing literature that shows that sensitivity to delayed food- and food-related outcomes is likely a fundamental process of obesity. Together, these data expand the animal model in a manner that better characterizes how environmental factors influence food consumption. PMID:26923097

Observation of creep behavior of cellulose electro-active paper (EAPap) actuator

NASA Astrophysics Data System (ADS)

Kim, Joo-Hyung; Lee, Sang-Woo; Yun, Gyu-Young; Yang, Chulho; Kim, Heung Soo; Kim, Jaehwan

2009-03-01

Understanding of creep effects on actuating mechanisms is important to precisely figure out the behavior of material. Creep behaviors of cellulose based Electro-Active Paper (EAPap) were studied under different constant loading conditions. We found the structural modification of microfibrils in EAPap after creep test. Structural differences of as-prepared and after creep tested samples were compared by SEM measurements. From the measured creep behaviors by different loading conditions, two different regions of induced strain and current were clearly observed as the measurement time increased. It is consider that local defects may occur and becomes micro-dimple or micro-crack formations in lower load cases as localized deformation proceeds, while the shrinkage of diameter of elongated fibers was observed only at the high level of loading. Therefore, cellulose nanofibers may play a role to be against the creep load and prevent the localized structural deformations. The results provide useful creep behavior and mechanism to understand the mechanical behavior of thin visco-elastic EAPap actuator.

Benefits of detailed models of muscle activation and mechanics

NASA Technical Reports Server (NTRS)

Lehman, S. L.; Stark, L.

1981-01-01

Recent biophysical and physiological studies identified some of the detailed mechanisms involved in excitation-contraction coupling, muscle contraction, and deactivation. Mathematical models incorporating these mechanisms allow independent estimates of key parameters, direct interplay between basic muscle research and the study of motor control, and realistic model behaviors, some of which are not accessible to previous, simpler, models. The existence of previously unmodeled behaviors has important implications for strategies of motor control and identification of neural signals. New developments in the analysis of differential equations make the more detailed models feasible for simulation in realistic experimental situations.

Fatigue behavior of a cross-ply ceramic matrix composite at elevated temperature under tension-tension loading. Master`s thesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steiner, C.D.

This study investigated the fatigue behavior and damage mechanisms of a (0/90)4s SiC/MAS ceramic matrix composite under tension-tension loading at two elevated temperatures and two frequencies. Stress and strain hystereses, maximum and minimum strain, and modulus of elasticity were evaluated to characterize the material behavior. Microscopy and fractography were used to evaluate damage progression and mechanisms. Fatigue life was independent of frequency at both temperatures.

Functions of behavior change interventions when implementing multi-professional teamwork at an emergency department: a comparative case study

PubMed Central

2014-01-01

Background While there is strong support for the benefits of working in multi-professional teams in health care, the implementation of multi-professional teamwork is reported to be complex and challenging. Implementation strategies combining multiple behavior change interventions are recommended, but the understanding of how and why the behavior change interventions influence staff behavior is limited. There is a lack of studies focusing on the functions of different behavior change interventions and the mechanisms driving behavior change. In this study, applied behavior analysis is used to analyze the function and impact of different behavior change interventions when implementing multi-professional teamwork. Methods A comparative case study design was applied. Two sections of an emergency department implemented multi-professional teamwork involving changes in work processes, aimed at increasing inter-professional collaboration. Behavior change interventions and staff behavior change were studied using observations, interviews and document analysis. Using a hybrid thematic analysis, the behavior change interventions were categorized according to the DCOM® model. The functions of the behavior change interventions were then analyzed using applied behavior analysis. Results The two sections used different behavior change interventions, resulting in a large difference in the degree of staff behavior change. The successful section enabled staff performance of teamwork behaviors with a strategy based on ongoing problem-solving and frequent clarification of directions. Managerial feedback initially played an important role in motivating teamwork behaviors. Gradually, as staff started to experience positive outcomes of the intervention, motivation for teamwork behaviors was replaced by positive task-generated feedback. Conclusions The functional perspective of applied behavior analysis offers insight into the behavioral mechanisms that describe how and why behavior change interventions influence staff behavior. The analysis demonstrates how enabling behavior change interventions, managerial feedback and task-related feedback interact in their influence on behavior and have complementary functions during different stages of implementation. PMID:24885212

Chemical kinetic reaction mechanism for the combustion of propane

NASA Technical Reports Server (NTRS)

Jachimowski, C. J.

1984-01-01

A detailed chemical kinetic reaction mechanism for the combustion of propane is presented and discussed. The mechanism consists of 27 chemical species and 83 elementary chemical reactions. Ignition and combustion data as determined in shock tube studies were used to evaluate the mechanism. Numerical simulation of the shock tube experiments showed that the kinetic behavior predicted by the mechanism for stoichiometric mixtures is in good agrement with the experimental results over the entire temperature range examined (1150-2600K). Sensitivity and theoretical studies carried out using the mechanism revealed that hydrocarbon reactions which are involved in the formation of the HO2 radical and the H2O2 molecule are very important in the mechanism and that the observed nonlinear behavior of ignition delay time with decreasing temperature can be interpreted in terms of the increased importance of the HO2 and H2O2 reactions at the lower temperatures.

High strain rate behavior of a SiC particulate reinforced Al{sub 2}O{sub 3} ceramic matrix composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, I.W.; Guden, M.

The high strain rate deformation behavior of composite materials is important for several reasons. First, knowledge of the mechanical properties of composites at high strain rates is needed for designing with these materials in applications where sudden changes in loading rates are likely to occur. Second, knowledge of both the dynamic and quasi-static mechanical responses can be used to establish the constitutive equations which are necessary to increase the confidence limits of these materials, particularly if they are to be used in critical structural applications. Moreover, dynamic studies and the knowledge gained form them are essential for the further developmentmore » of new material systems for impact applications. In this study, the high strain rate compressive deformation behavior of a ceramic matrix composite (CMC) consisting of SiC particles and an Al{sub 2}O{sub 3} matrix was studied and compared with its quasi-static behavior. Microscopic observations were conducted to investigate the deformation and fracture mechanism of the composite.« less

Determinants of First-Time Cancer Examinations in a Rural Community: A Mechanism for Behavior Change

PubMed Central

Guo, Yi; Emanuel, Amber S.; Shepperd, James A.; Dodd, Virginia J.; Marks, John G.; Muller, Keith E.; Riley, Joseph L.

2015-01-01

Objectives. After conducting a media campaign focusing on the importance of oral and pharyngeal cancer (OPC) examinations, we assessed mechanisms of behavior change among individuals receiving an OPC examination for the first time. Methods. We used data from 2 waves of telephone surveys of individuals residing in 36 rural census tracts in northern Florida (n = 806). The second survey occurred after our media intervention. We developed media messages and modes of message delivery with community members via focus groups and intercept interviews. We performed a mediation analysis to examine behavior change mechanisms. Results. Greater exposure to media messages corresponded with heightened concern about OPC. Heightened concern, in turn, predicted receipt of a first-time OPC examination, but only among men. Conclusions. We extended earlier studies by measuring an outcome behavior (receipt of an OPC examination) and demonstrating that the putative mechanism of action (concern about the disease) explained the link between a media intervention and engaging in the target behavior. Improving the quality of media campaigns by engaging community stakeholders in selecting messages and delivery methods is an effective strategy in building public health interventions aimed at changing behaviors. PMID:25973820

Walnuts improve neuronal and behavioral function in aging

USDA-ARS?s Scientific Manuscript database

Introduction Walnuts are rich in polyunsaturated fatty acids (PUFAs) and polyphenols which have been shown to improve neurochemical and behavioral function. Objectives This study investigated the mechanisms associated with age-related behavioral improvements in rats fed diets supplemented with walnu...

Online monitoring of corrosion behavior in molten metal using laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Zeng, Qiang; Pan, Congyuan; Li, Chaoyang; Fei, Teng; Ding, Xiaokang; Du, Xuewei; Wang, Qiuping

2018-04-01

The corrosion behavior of structure materials in direct contact with molten metals is widespread in metallurgical industry. The corrosion of casting equipment by molten metals is detrimental to the production process, and the corroded materials can also contaminate the metals being produced. Conventional methods for studying the corrosion behavior by molten metal are offline. This work explored the application of laser-induced breakdown spectroscopy (LIBS) for online monitoring of the corrosion behavior of molten metal. The compositional changes of molten aluminum in crucibles made of 304 stainless steel were obtained online at 1000 °C. Several offline techniques were combined to determine the corrosion mechanism, which was highly consistent with previous studies. Results proved that LIBS was an efficient method to study the corrosion mechanism of solid materials in molten metal.

Verhalten und Neurobiologie von stimmbegabten Insekten

NASA Astrophysics Data System (ADS)

Huber, Franz

1992-09-01

Crickets, tettigoniids (bush crickets or long-horned grasshoppers) and acridids (short-horned grasshoppers) are well-suited animals to study acoustically mediated behavior and to search for the underlying sensory, nervous, and effector mechanisms. Several behavioral tactics are described which improve reproductive success, serve to avoid predators such as bats, or have been developed for defence against parasitic insects. Phonotactic orientation of female crickets toward the calling male was chosen, since for this behavior the underlying sensory and nervous mechanisms have been intensively studied. Song recognition was found to be based on one critical parameter of the song, the syllable period, and the females show a bandpass behavior for which a correlate exists in local brain neurons. Sound orientation is based on a pressure gradient mechanism in each ear, and it needs a binaural intensity comparison within the central nervous system. With intracellular recordings from auditory interneurons during phonotactic orientation and their manipulation, a cellular correlate could be found which obeys the rule “ turn to the side most strongly stimulated”.

Dendritic Spines in Depression: What We Learned from Animal Models

PubMed Central

Qiao, Hui; Li, Ming-Xing; Xu, Chang; Chen, Hui-Bin; An, Shu-Cheng; Ma, Xin-Ming

2016-01-01

Depression, a severe psychiatric disorder, has been studied for decades, but the underlying mechanisms still remain largely unknown. Depression is closely associated with alterations in dendritic spine morphology and spine density. Therefore, understanding dendritic spines is vital for uncovering the mechanisms underlying depression. Several chronic stress models, including chronic restraint stress (CRS), chronic unpredictable mild stress (CUMS), and chronic social defeat stress (CSDS), have been used to recapitulate depression-like behaviors in rodents and study the underlying mechanisms. In comparison with CRS, CUMS overcomes the stress habituation and has been widely used to model depression-like behaviors. CSDS is one of the most frequently used models for depression, but it is limited to the study of male mice. Generally, chronic stress causes dendritic atrophy and spine loss in the neurons of the hippocampus and prefrontal cortex. Meanwhile, neurons of the amygdala and nucleus accumbens exhibit an increase in spine density. These alterations induced by chronic stress are often accompanied by depression-like behaviors. However, the underlying mechanisms are poorly understood. This review summarizes our current understanding of the chronic stress-induced remodeling of dendritic spines in the hippocampus, prefrontal cortex, orbitofrontal cortex, amygdala, and nucleus accumbens and also discusses the putative underlying mechanisms. PMID:26881133

Nociceptor Sensitization Depends on Age and Pain Chronicity123

PubMed Central

Dodge, Amanda K.

2016-01-01

Abstract Peripheral inflammation causes mechanical pain behavior and increased action potential firing. However, most studies examine inflammatory pain at acute, rather than chronic time points, despite the greater burden of chronic pain on patient populations, especially aged individuals. Furthermore, there is disagreement in the field about whether primary afferents contribute to chronic pain. Therefore, we sought to evaluate the contribution of nociceptor activity to the generation of pain behaviors during the acute and chronic phases of inflammation in both young and aged mice. We found that both young (2 months old) and aged (>18 months old) mice exhibited prominent pain behaviors during both acute (2 day) and chronic (8 week) inflammation. However, young mice exhibited greater behavioral sensitization to mechanical stimuli than their aged counterparts. Teased fiber recordings in young animals revealed a twofold mechanical sensitization in C fibers during acute inflammation, but an unexpected twofold reduction in firing during chronic inflammation. Responsiveness to capsaicin and mechanical responsiveness of A-mechanonociceptor (AM) fibers were also reduced chronically. Importantly, this lack of sensitization in afferent firing during chronic inflammation occurred even as these inflamed mice exhibited continued behavioral sensitization. Interestingly, C fibers from inflamed aged animals showed no change in mechanical firing compared with controls during either the acute or chronic inflammatory phases, despite strong behavioral sensitization to mechanical stimuli at these time points. These results reveal the following two important findings: (1) nociceptor sensitization to mechanical stimulation depends on age and the chronicity of injury; and (2) maintenance of chronic inflammatory pain does not rely on enhanced peripheral drive. PMID:26866058

Fracture behaviors under pure shear loading in bulk metallic glasses

NASA Astrophysics Data System (ADS)

Chen, Cen; Gao, Meng; Wang, Chao; Wang, Wei-Hua; Wang, Tzu-Chiang

2016-12-01

Pure shear fracture test, as a special mechanical means, had been carried out extensively to obtain the critical information for traditional metallic crystalline materials and rocks, such as the intrinsic deformation behavior and fracture mechanism. However, for bulk metallic glasses (BMGs), the pure shear fracture behaviors have not been investigated systematically due to the lack of a suitable test method. Here, we specially introduce a unique antisymmetrical four-point bend shear test method to realize a uniform pure shear stress field and study the pure shear fracture behaviors of two kinds of BMGs, Zr-based and La-based BMGs. All kinds of fracture behaviors, the pure shear fracture strength, fracture angle and fracture surface morphology, are systematically analyzed and compared with those of the conventional compressive and tensile fracture. Our results indicate that both the Zr-based and La-based BMGs follow the same fracture mechanism under pure shear loading, which is significantly different from the situation of some previous research results. Our results might offer new enlightenment on the intrinsic deformation and fracture mechanism of BMGs and other amorphous materials.

Fracture behaviors under pure shear loading in bulk metallic glasses.

PubMed

Chen, Cen; Gao, Meng; Wang, Chao; Wang, Wei-Hua; Wang, Tzu-Chiang

2016-12-23

Pure shear fracture test, as a special mechanical means, had been carried out extensively to obtain the critical information for traditional metallic crystalline materials and rocks, such as the intrinsic deformation behavior and fracture mechanism. However, for bulk metallic glasses (BMGs), the pure shear fracture behaviors have not been investigated systematically due to the lack of a suitable test method. Here, we specially introduce a unique antisymmetrical four-point bend shear test method to realize a uniform pure shear stress field and study the pure shear fracture behaviors of two kinds of BMGs, Zr-based and La-based BMGs. All kinds of fracture behaviors, the pure shear fracture strength, fracture angle and fracture surface morphology, are systematically analyzed and compared with those of the conventional compressive and tensile fracture. Our results indicate that both the Zr-based and La-based BMGs follow the same fracture mechanism under pure shear loading, which is significantly different from the situation of some previous research results. Our results might offer new enlightenment on the intrinsic deformation and fracture mechanism of BMGs and other amorphous materials.

Influence of compression parameters on mechanical behavior of mozzarella cheese.

PubMed

Fogaça, Davi Novaes Ladeia; da Silva, William Soares; Rodrigues, Luciano Brito

2017-10-01

Studies on the interaction between direction and degree of compression in the Texture Profile Analysis (TPA) of cheeses are limited. For this reason the present study aimed to evaluate the mechanical properties of Mozzarella cheese by TPA at different compression degrees (65, 75, and 85%) and directions (axes X, Y, and Z). Data obtained were compared in order to identify possible interaction between both factors. Compression direction did not affect any mechanical variable, or rather, the cheese had an isotropic behavior for TPA. Compression degree had a significant influence (p < 0.05) on TPA responses, excepting for chewiness TPA (N), which remained constant. Data from texture profile were adjusted to models to explain the mechanical behavior according to the compression degree used in the test. The isotropic behavior observed may be result of differences in production method of Mozzarella cheese especially on stretching of cheese mass. Texture Profile Analysis (TPA) is a technique largely used to assess the mechanical properties of food, particularly cheese. The precise choice of the instrumental test configuration is essential for achieving results that represent the material analyzed. The method of manufacturing is another factor that may directly influence the mechanical properties of food. This can be seen, for instance, in stretched curd cheese, such as Mozzarella. Knowledge on such mechanical properties is highly relevant for food industries due to the mechanical resistance in piling, pressing, manufacture of packages, and food transport, or to melting features presented by the food at high temperatures in preparation of several foods, such as pizzas, snacks, sandwiches, and appetizers. © 2016 Wiley Periodicals, Inc.

Mechanical Properties of Additively Manufactured Thick Honeycombs

PubMed Central

Hedayati, Reza; Sadighi, Mojtaba; Mohammadi Aghdam, Mohammad; Zadpoor, Amir Abbas

2016-01-01

Honeycombs resemble the structure of a number of natural and biological materials such as cancellous bone, wood, and cork. Thick honeycomb could be also used for energy absorption applications. Moreover, studying the mechanical behavior of honeycombs under in-plane loading could help understanding the mechanical behavior of more complex 3D tessellated structures such as porous biomaterials. In this paper, we study the mechanical behavior of thick honeycombs made using additive manufacturing techniques that allow for fabrication of honeycombs with arbitrary and precisely controlled thickness. Thick honeycombs with different wall thicknesses were produced from polylactic acid (PLA) using fused deposition modelling, i.e., an additive manufacturing technique. The samples were mechanically tested in-plane under compression to determine their mechanical properties. We also obtained exact analytical solutions for the stiffness matrix of thick hexagonal honeycombs using both Euler-Bernoulli and Timoshenko beam theories. The stiffness matrix was then used to derive analytical relationships that describe the elastic modulus, yield stress, and Poisson’s ratio of thick honeycombs. Finite element models were also built for computational analysis of the mechanical behavior of thick honeycombs under compression. The mechanical properties obtained using our analytical relationships were compared with experimental observations and computational results as well as with analytical solutions available in the literature. It was found that the analytical solutions presented here are in good agreement with experimental and computational results even for very thick honeycombs, whereas the analytical solutions available in the literature show a large deviation from experimental observation, computational results, and our analytical solutions. PMID:28773735

Evaluation of disintegration properties of orally rapidly disintegrating tablets using a novel disintegration tester.

PubMed

Kondo, Keita; Niwa, Toshiyuki; Danjo, Kazumi

2012-01-01

This report describes a new disintegration tester that can determine not only the disintegration time of orally rapidly disintegrating tablets (ODT), but also the disintegration behavior and mechanism. Using the tester, the disintegration properties of the tablets prepared in a previous study were examined. The purpose of this study is to confirm the utility of the tester as an instrument for evaluating the disintegration properties of ODT and determine relations among time, behavior and mechanism of the disintegration. Results demonstrated that in vitro disintegration time in the tester is similar to that in the commercial disintegration tester for ODT and is highly correlated with oral disintegration time. Observations of disintegration process revealed that a difference in disintegration behavior between tablets compressed at 50-75 MPa and 100 MPa; the disintegration behavior of the tablets were designated immediate disintegrating type and gradual disintegrating type, respectively. The dynamic swelling profile and water absorption profile indicated that the disintegration mechanism of the tablets involved wicking action induced by swelling of the disintegrant; the disintegration time was closely related to the initial rates of swelling and water absorption. Furthermore, the mechanism of water absorption of tablets compressed at 50-75 MPa and 100 MPa shows anomalous diffusion and case-II transport, respectively. The shift in this mechanism is consistent with differences in disintegration time and behavior between the tablets. These findings suggest that information on disintegration properties obtained by our tester is useful for understanding of disintegration phenomena of ODT.

From Solidification Processing to Microstructure to Mechanical Properties: A Multi-scale X-ray Study of an Al-Cu Alloy Sample

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tourret, D.; Mertens, J. C. E.; Lieberman, E.

We follow an Al-12 at. pct Cu alloy sample from the liquid state to mechanical failure, using in situ X-ray radiography during directional solidification and tensile testing, as well as three-dimensional computed tomography of the microstructure before and after mechanical testing. The solidification processing stage is simulated with a multi-scale dendritic needle network model, and the micromechanical behavior of the solidified microstructure is simulated using voxelized tomography data and an elasto-viscoplastic fast Fourier transform model. This study demonstrates the feasibility of direct in situ monitoring of a metal alloy microstructure from the liquid processing stage up to its mechanical failure,more » supported by quantitative simulations of microstructure formation and its mechanical behavior.« less

From Solidification Processing to Microstructure to Mechanical Properties: A Multi-scale X-ray Study of an Al-Cu Alloy Sample

DOE PAGES

Tourret, D.; Mertens, J. C. E.; Lieberman, E.; ...

2017-09-13

We follow an Al-12 at. pct Cu alloy sample from the liquid state to mechanical failure, using in situ X-ray radiography during directional solidification and tensile testing, as well as three-dimensional computed tomography of the microstructure before and after mechanical testing. The solidification processing stage is simulated with a multi-scale dendritic needle network model, and the micromechanical behavior of the solidified microstructure is simulated using voxelized tomography data and an elasto-viscoplastic fast Fourier transform model. This study demonstrates the feasibility of direct in situ monitoring of a metal alloy microstructure from the liquid processing stage up to its mechanical failure,more » supported by quantitative simulations of microstructure formation and its mechanical behavior.« less

From Solidification Processing to Microstructure to Mechanical Properties: A Multi-scale X-ray Study of an Al-Cu Alloy Sample

NASA Astrophysics Data System (ADS)

Tourret, D.; Mertens, J. C. E.; Lieberman, E.; Imhoff, S. D.; Gibbs, J. W.; Henderson, K.; Fezzaa, K.; Deriy, A. L.; Sun, T.; Lebensohn, R. A.; Patterson, B. M.; Clarke, A. J.

2017-11-01

We follow an Al-12 at. pct Cu alloy sample from the liquid state to mechanical failure, using in situ X-ray radiography during directional solidification and tensile testing, as well as three-dimensional computed tomography of the microstructure before and after mechanical testing. The solidification processing stage is simulated with a multi-scale dendritic needle network model, and the micromechanical behavior of the solidified microstructure is simulated using voxelized tomography data and an elasto-viscoplastic fast Fourier transform model. This study demonstrates the feasibility of direct in situ monitoring of a metal alloy microstructure from the liquid processing stage up to its mechanical failure, supported by quantitative simulations of microstructure formation and its mechanical behavior.

High quality factor indium oxide mechanical microresonators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartolomé, Javier, E-mail: j.bartolome@fis.ucm.es; Cremades, Ana; Piqueras, Javier

2015-11-09

The mechanical resonance behavior of as-grown In{sub 2}O{sub 3} microrods has been studied in this work by in-situ scanning electron microscopy (SEM) electrically induced mechanical oscillations. Indium oxide microrods grown by a vapor–solid method are naturally clamped to an aluminum oxide ceramic substrate, showing a high quality factor due to reduced energy losses during mechanical vibrations. Quality factors of more than 10{sup 5} and minimum detectable forces of the order of 10{sup −16} N/Hz{sup 1/2} demonstrate their potential as mechanical microresonators for real applications. Measurements at low-vacuum using the SEM environmental operation mode were performed to study the effect ofmore » extrinsic damping on the resonators behavior. The damping coefficient has been determined as a function of pressure.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Esfahani, M. Nasr; Yilmaz, M.; Sonne, M. R.

The trend towards nanomechanical resonator sensors with increasing sensitivity raises the need to address challenges encountered in the modeling of their mechanical behavior. Selecting the best approach in mechanical response modeling amongst the various potential computational solid mechanics methods is subject to controversy. A guideline for the selection of the appropriate approach for a specific set of geometry and mechanical properties is needed. In this study, geometrical limitations in frequency response modeling of flexural nanomechanical resonators are investigated. Deviation of Euler and Timoshenko beam theories from numerical techniques including finite element modeling and Surface Cauchy-Born technique are studied. The resultsmore » provide a limit beyond which surface energy contribution dominates the mechanical behavior. Using the Surface Cauchy-Born technique as the reference, a maximum error on the order of 50 % is reported for high-aspect ratio resonators.« less

Effects of behavioral activation on default mode network connectivity in subthreshold depression: A preliminary resting-state fMRI study.

PubMed

Yokoyama, Satoshi; Okamoto, Yasumasa; Takagaki, Koki; Okada, Go; Takamura, Masahiro; Mori, Asako; Shiota, Syouichi; Ichikawa, Naho; Jinnin, Ran; Yamawaki, Shigeto

2018-02-01

Subthreshold depression is a risk factor for major depressive disorder, and it is known to have a negative impact on quality of life (QOL). Although behavioral activation, which is one type of cognitive behavioral therapy, is an effective psychological intervention for subthreshold depression, neural mechanisms of behavioral activation are unclear. Enhanced functional connectivity between default mode network (DMN) and the other regions has been demonstrated in participants with subthreshold depression. The purpose of this study was to examine the effects of behavioral activation on DMN abnormalities by using resting-state functional MRI (rs-fMRI). Participants with subthreshold depression (N =40) were randomly assigned to either an intervention group or a non-intervention group. They were scanned using rs-fMRI before and after the intervention. Independent component analysis indicated three subnetworks of the DMN. Analyzing intervention effects on functional connectivity of each subnetwork indicated that connectivity of the anterior DMN subnetwork with the dorsal anterior cingulate was reduced after the intervention. Moreover, this reduction was correlated with an increase in health-related QOL. We did not compare the findings with healthy participants. Further research should be conducted by including healthy controls to verify the results of this study. Mechanisms of behavioral activation might be related to enhanced ability to independently use the dACC and the DMN, which increases an attention control to positive external stimuli. This is the first study to investigate neural mechanisms of behavioral activation using rs-fMRI. Copyright © 2017 Elsevier B.V. All rights reserved.

Endocrine and neuroendocrine regulation of fathering behavior in birds.

PubMed

Lynn, Sharon E

2016-01-01

This article is part of a Special Issue "Parental Care". Although paternal care is generally rare among vertebrates, care of eggs and young by male birds is extremely common and may take on a variety of forms across species. Thus, birds provide ample opportunities for investigating both the evolution of and the proximate mechanisms underpinning diverse aspects of fathering behavior. However, significant gaps remain in our understanding of the endocrine and neuroendocrine influences on paternal care in this vertebrate group. In this review, I focus on proximate mechanisms of paternal care in birds. I place an emphasis on specific hormones that vary predictably and/or unpredictably during the parental phase in both captive and wild birds: prolactin and progesterone are generally assumed to enhance paternal care, whereas testosterone and corticosterone are commonly-though not always correctly-assumed to inhibit paternal care. In addition, because endocrine secretions are not the sole mechanistic influence on paternal behavior, I also explore potential roles for certain neuropeptide systems (specifically the oxytocin-vasopressin nonapeptides and gonadotropin inhibitory hormone) and social and experiential factors in influencing paternal behavior in birds. Ultimately, mechanistic control of fathering behavior in birds is complex, and I suggest specific avenues for future research with the goal of narrowing gaps in our understanding of this complexity. Such avenues include (1) experimental studies that carefully consider not only endocrine and neuroendocrine mechanisms of paternal behavior, but also the ecology, phylogenetic history, and social context of focal species; (2) investigations that focus on individual variation in both hormonal and behavioral responses during the parental phase; (3) studies that investigate mechanisms of maternal and paternal care independently, rather than assuming that the mechanistic foundations of care are similar between the sexes; (4) expansion of work on interactions of the neuroendocrine system and fathering behavior to a wider array of paternal behaviors and taxa (e.g., currently, studies of the interactions of testosterone and paternal care largely focus on songbirds, whereas studies of the interactions of corticosterone, prolactin, and paternal care in times of stress focus primarily on seabirds); and (5) more deliberate study of exceptions to commonly held assumptions about hormone-paternal behavior interactions (such as the prevailing assumptions that elevations in androgens and glucocorticoids are universally disruptive to paternal care). Ultimately, investigations that take an intentionally integrative approach to understanding the social, evolutionary, and physiological influences on fathering behavior will make great strides toward refining our understanding of the complex nature by which paternal behavior in birds is regulated. Copyright © 2015 Elsevier Inc. All rights reserved.

Impact compaction of a granular material

DOE PAGES

Fenton, Gregg; Asay, Blaine; Dalton, Devon

2015-05-19

The dynamic behavior of granular materials has importance to a variety of engineering applications. Structural seismic coupling, planetary science, and earth penetration mechanics, are just a few of the application areas. Although the mechanical behavior of granular materials of various types have been studied extensively for several decades, the dynamic behavior of such materials remains poorly understood. High-quality experimental data are needed to improve our general understanding of granular material compaction physics. This study will describe how an instrumented plunger impact system can be used to measure pressure-density relationships for model materials at high and controlled strain rates and subsequentlymore » used for computational modeling.« less

The Association of Birth Complications and Externalizing Behavior in Early Adolescents: Direct and Mediating Effects

ERIC Educational Resources Information Center

Liu, Jianghong; Raine, Adrian; Wuerker, Anne; Venables, Peter H.; Mednick, Sarnoff

2009-01-01

Prior studies have shown that birth complications interact with psychosocial risk factors in predisposing to increased externalizing behavior in childhood and criminal behavior in adulthood. However, little is known about the direct relationship between birth complications and externalizing behavior. Furthermore, the mechanism by which the birth…

Fracture mechanics correlation of boron/aluminum coupons containing stress risers

NASA Technical Reports Server (NTRS)

Adsit, N. R.; Waszczak, J. P.

1975-01-01

The mechanical behavior of boron/aluminum near stress risers has been studied and reported. This effort was directed toward defining the tensile behavior of both unidirectional and (0/ plus or minus 45) boron/aluminum using linear elastic fracture mechanics (LEFM). The material used was 5.6-mil boron in 6061 aluminum, consolidated using conventional diffusion bonding techniques. Mechanical properties are reported for both unidirectional and (0/ plus or minus 45) boron/aluminum, which serve as control data for the fracture mechanics predictions. Three different flawed specimen types were studied. In each case the series of specimens remained geometrically similar to eliminate variations in finite size correction factors. The fracture data from these tests were reduced using two techniques. They both used conventional LEFM methods, but the existence of a characteristic flaw was assumed in one case and not the other. Both the data and the physical behavior of the specimens support the characteristic flaw hypothesis. Cracks were observed growing slowly in the (0/ plus or minus 45) laminates, until a critical crack length was reached at which time catastrophic failure occurred.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Chao; Xu, Jun; Cao, Lei

The electrodes of lithium-ion batteries (LIB) are known to be brittle and to fail earlier than the separators during an external crush event. Thus, the understanding of mechanical failure mechanism for LIB electrodes (anode and cathode) is critical for the safety design of LIB cells. In this paper, we present experimental and numerical studies on the constitutive behavior and progression of failure in LIB electrodes. Mechanical tests were designed and conducted to evaluate the constitutive properties of porous electrodes. Constitutive models were developed to describe the stress-strain response of electrodes under uniaxial tensile and compressive loads. The failure criterion andmore » a damage model were introduced to model their unique tensile and compressive failure behavior. The failure mechanism of LIB electrodes was studied using the blunt rod test on dry electrodes, and numerical models were built to simulate progressive failure. The different failure processes were examined and analyzed in detail numerically, and correlated with experimentally observed failure phenomena. Finally, the test results and models improve our understanding of failure behavior in LIB electrodes, and provide constructive insights on future development of physics-based safety design tools for battery structures under mechanical abuse.« less

Mechanism by which BMI influences leisure-time physical activity behavior.

PubMed

Godin, Gaston; Bélanger-Gravel, Ariane; Nolin, Bertrand

2008-06-01

The objective of this prospective study was to clarify the mechanism by which BMI influences leisure-time physical activity. This was achieved in accordance with the assumptions underlying the Theory of Planned Behavior (TPB), considered as one of the most useful theories to predict behavior adoption. At baseline, a sample of 1,530 respondents completed a short questionnaire to measure intention and perceived behavioral control (PBC), the two proximal determinants of behavior of TPB. Past behavior, sociodemographic variables, and weight and height were also assessed. The dependent variable, leisure-time physical activity was assessed 3 months later. Hierarchical multiple regression analyses revealed that BMI is a direct predictor of future leisure-time physical activity, not mediated by the variables of TPB. Additional hierarchical analyses indicated that BMI was not a moderator of the intention-behavior and PBC-behavior relationships. The results of this study suggest that high BMI is a significant negative determinant of leisure-time physical activity. This observation reinforces the importance of preventing weight gain as a health promotion strategy for avoiding a sedentary lifestyle.

A review of cetacean lung morphology and mechanics.

PubMed

Piscitelli, Marina A; Raverty, Stephen A; Lillie, Margo A; Shadwick, Robert E

2013-12-01

Cetaceans possess diverse adaptations in respiratory structure and mechanics that are highly specialized for an array of surfacing and diving behaviors. Some of these adaptations and air management strategies are still not completely understood despite over a century of study. We have compiled the historical and contemporary knowledge of cetacean lung anatomy and mechanics in regards to normal lung function during ventilation and air management while diving. New techniques are emerging utilizing pulmonary mechanics to measure lung function in live cetaceans. Given the diversity of respiratory adaptations in cetaceans, interpretations of these results should consider species-specific anatomy, mechanics, and behavior. Copyright © 2013 Wiley Periodicals, Inc.

A Quantitative Study of the Relationship between the Distribution of Different Types of Collagen and the Mechanical Behavior of Rabbit Medial Collateral Ligaments

PubMed Central

Wan, Chao; Hao, Zhixiu; Wen, Shizhu; Leng, Huijie

2014-01-01

The mechanical properties of ligaments are key contributors to the stability and function of musculoskeletal joints. Ligaments are generally composed of ground substance, collagen (mainly type I and III collagen), and minimal elastin fibers. However, no consensus has been reached about whether the distribution of different types of collagen correlates with the mechanical behaviors of ligaments. The main objective of this study was to determine whether the collagen type distribution is correlated with the mechanical properties of ligaments. Using axial tensile tests and picrosirius red staining-polarization observations, the mechanical behaviors and the ratios of the various types of collagen were investigated for twenty-four rabbit medial collateral ligaments from twenty-four rabbits of different ages, respectively. One-way analysis of variance was used in the comparison of the Young's modulus in the linear region of the stress-strain curves and the ratios of type I and III collagen for the specimens (the mid-substance specimens of the ligaments) with different ages. A multiple linear regression was performed using the collagen contents (the ratios of type I and III collagen) and the Young's modulus of the specimens. During the maturation of the ligaments, the type I collagen content increased, and the type III collagen content decreased. A significant and strong correlation () was identified by multiple linear regression between the collagen contents (i.e., the ratios of type I and type III collagen) and the mechanical properties of the specimens. The collagen content of ligaments might provide a new perspective for evaluating the linear modulus of global stress-strain curves for ligaments and open a new door for studying the mechanical behaviors and functions of connective tissues. PMID:25062068

A quantitative study of the relationship between the distribution of different types of collagen and the mechanical behavior of rabbit medial collateral ligaments.

PubMed

Wan, Chao; Hao, Zhixiu; Wen, Shizhu; Leng, Huijie

2014-01-01

The mechanical properties of ligaments are key contributors to the stability and function of musculoskeletal joints. Ligaments are generally composed of ground substance, collagen (mainly type I and III collagen), and minimal elastin fibers. However, no consensus has been reached about whether the distribution of different types of collagen correlates with the mechanical behaviors of ligaments. The main objective of this study was to determine whether the collagen type distribution is correlated with the mechanical properties of ligaments. Using axial tensile tests and picrosirius red staining-polarization observations, the mechanical behaviors and the ratios of the various types of collagen were investigated for twenty-four rabbit medial collateral ligaments from twenty-four rabbits of different ages, respectively. One-way analysis of variance was used in the comparison of the Young's modulus in the linear region of the stress-strain curves and the ratios of type I and III collagen for the specimens (the mid-substance specimens of the ligaments) with different ages. A multiple linear regression was performed using the collagen contents (the ratios of type I and III collagen) and the Young's modulus of the specimens. During the maturation of the ligaments, the type I collagen content increased, and the type III collagen content decreased. A significant and strong correlation (R2 = 0.839, P < 0.05) was identified by multiple linear regression between the collagen contents (i.e., the ratios of type I and type III collagen) and the mechanical properties of the specimens. The collagen content of ligaments might provide a new perspective for evaluating the linear modulus of global stress-strain curves for ligaments and open a new door for studying the mechanical behaviors and functions of connective tissues.

Investigation of Mechanisms of Viscoelastic Behavior of Collagen Molecule

PubMed Central

Ghodsi, Hossein; Darvish, Kurosh

2015-01-01

Unique mechanical properties of collagen molecule make it one of the most important and abundant proteins in animals. Many tissues such as connective tissues rely on these properties to function properly. In the past decade, molecular dynamics (MD) simulations have been used extensively to study the mechanical behavior of molecules. For collagen, MD simulations were primarily used to determine its elastic properties. In this study, constant force steered MD simulations were used to perform creep tests on collagen molecule segments. The mechanical behavior of the segments, with lengths of approximately 20 (1X), 38 (2X), 74 (4X), and 290 nm (16X), was characterized using a quasi-linear model to describe the observed viscoelastic responses. To investigate the mechanisms of the viscoelastic behavior, hydrogen bonds (H-bonds) rupture/formation time history of the segments were analyzed and it was shown that the formation growth rate of H-bonds in the system is correlated with the creep growth rate of the segment ( β = 2.41 βH). In addition, a linear relationship between H-bonds formation growth rate and the length of the segment was quantified. Based on these findings, a general viscoelastic model was developed and verified where, using the smallest segment as a building block, the viscoelastic properties of larger segments could be predicted. In addition, the effect of temperature control methods on the mechanical properties were studied, and it was shown that application of Langevin Dynamics had adverse effect on these properties while the Lowe-Anderson method was shown to be more appropriate for this application. This study provides information that is essential for multi-scale modeling of collagen fibrils using a bottom-up approach. PMID:26256473

Investigation of mechanisms of viscoelastic behavior of collagen molecule.

PubMed

Ghodsi, Hossein; Darvish, Kurosh

2015-11-01

Unique mechanical properties of collagen molecule make it one of the most important and abundant proteins in animals. Many tissues such as connective tissues rely on these properties to function properly. In the past decade, molecular dynamics (MD) simulations have been used extensively to study the mechanical behavior of molecules. For collagen, MD simulations were primarily used to determine its elastic properties. In this study, constant force steered MD simulations were used to perform creep tests on collagen molecule segments. The mechanical behavior of the segments, with lengths of approximately 20 (1X), 38 (2X), 74 (4X), and 290 nm (16X), was characterized using a quasi-linear model to describe the observed viscoelastic responses. To investigate the mechanisms of the viscoelastic behavior, hydrogen bonds (H-bonds) rupture/formation time history of the segments were analyzed and it was shown that the formation growth rate of H-bonds in the system is correlated with the creep growth rate of the segment (β=2.41βH). In addition, a linear relationship between H-bonds formation growth rate and the length of the segment was quantified. Based on these findings, a general viscoelastic model was developed and verified here, using the smallest segment as a building block, the viscoelastic properties of larger segments could be predicted. In addition, the effect of temperature control methods on the mechanical properties were studied, and it was shown that application of Langevin Dynamics had adverse effect on these properties while the Lowe-Anderson method was shown to be more appropriate for this application. This study provides information that is essential for multi-scale modeling of collagen fibrils using a bottom-up approach. Copyright © 2015 Elsevier Ltd. All rights reserved.

Mediating Mechanisms of Theory-Based Psychosocial Determinants on Behavioral Changes in a Middle School Obesity Risk Reduction Curriculum Intervention, Choice, Control, and Change.

PubMed

Gray, Heewon Lee; Contento, Isobel R; Koch, Pamela A; Noia, Jennifer Di

2016-10-01

A limited number of school-based intervention studies have explored mediating mechanisms of theory-based psychosocial variables on obesity risk behavior changes. The current study investigated how theory-based psychosocial determinants mediated changes in energy balance-related behaviors (EBRBs) among urban youth. A secondary analysis study was conducted using data from a cluster randomized controlled trial. Data from students at 10 middle schools in New York City (n = 1136) were used. The intervention, Choice, Control, and Change curriculum, was based on social cognitive and self-determination theories. Theory-based psychosocial determinants (goal intention, cognitive outcome expectations, affective outcome expectations, self-efficacy, perceived barriers, and autonomous motivation) and EBRBs were measured with self-report questionnaires. Mediation mechanisms were examined using structural equation modeling, Results: Mediating mechanisms for daily sugar-sweetened beverage (SSB) consumption and purposeful stair climbing were identified. Models with best fit indices (root mean square error of approximation = 0.039/0.045, normed fit index = 0.916/0.882; comparative fit index = 0.945/0.932; Tucker-Lewis index = 0.896/0.882, respectively) suggested that goal intention and reduced perceived barriers were significant proximal mediators for reducing SSB consumption among both boys and girls or increasing physical activity by stair climbing among boys. Cognitive outcome expectations, affective outcome expectations, self-efficacy, and autonomous motivation indirectly mediated behavioral changes through goal intention or perceived barriers (p < 0.05 to p < 0.001). The final models explained 25%-27% of behavioral outcome variances. Theory-based psychosocial determinants targeted in Choice, Control, and Change in fact mediated behavior changes in middle school students. Strategies targeting these mediators might benefit future success of behavioral interventions. Further studies are needed to determine other potential mediators of EBRBs in youth.

Dispersion Strengthening.

DTIC Science & Technology

1987-07-27

June 1979. 22. p - V S~* ~~ " 17. " Strengthening Mechanisms in Martensitic Steels ", Peking University Institute for Iron and Steel Technology...directed towards studying the strengthening behavior of nickel-base superalloys, the strengthening behavior of ferrous martensite , and the kinetics of...coherency strain is not a dominant strengthening mechanism in nickel-base super- alloys with low volume fractions of -y The important conclusions

First-order Description of the Mechanical Fracture Behavior of Fine-Grained Surficial Marine Sediments During Gas Bubble Growth

DTIC Science & Technology

2010-01-01

Mechanical analysis of idealized shallow hydraulic fracture, / Geotech . Geoenviron. Eng., 128, 488-495, doi:10.1061/ (ASCE) 1090-0241 (2002) 128:6(488...F. Chiu, and H.-J. Chai (2007), Experimental study on fracture behavior of a silty clay, Geotech . Test. J., 30, 1-9, doi: I0.1520/GTJI00715

Mechanism of Change in Cognitive-Behavioral Treatment of Panic Disorder: Evidence for the Fear of Fear Mediational Hypothesis

ERIC Educational Resources Information Center

Smits, Jasper A. J.; Powers, Mark B.; Cho, Yongrae; Telch, Michael J.

2004-01-01

Numerous clinical trials have demonstrated the efficacy of cognitive-behavioral treatment (CBT) for panic disorder. However, studies investigating the mechanisms responsible for improvement with CBT are lacking. The authors used regression analyses outlined by R. M. Baron and D. A. Kenny (1986) to test whether a reduction in fear of fear (FOF)…

Genetic and neuronal mechanisms governing the sex-specific interaction between sleep and sexual behaviors in Drosophila.

PubMed

Chen, Dandan; Sitaraman, Divya; Chen, Nan; Jin, Xin; Han, Caihong; Chen, Jie; Sun, Mengshi; Baker, Bruce S; Nitabach, Michael N; Pan, Yufeng

2017-07-28

Animals execute one particular behavior among many others in a context-dependent manner, yet the mechanisms underlying such behavioral choice remain poorly understood. Here we studied how two fundamental behaviors, sex and sleep, interact at genetic and neuronal levels in Drosophila. We show that an increased need for sleep inhibits male sexual behavior by decreasing the activity of the male-specific P1 neurons that coexpress the sex determination genes fru M and dsx, but does not affect female sexual behavior. Further, we delineate a sex-specific neuronal circuit wherein the P1 neurons encoding increased courtship drive suppressed male sleep by forming mutually excitatory connections with the fru M -positive sleep-controlling DN1 neurons. In addition, we find that FRU M regulates male courtship and sleep through distinct neural substrates. These studies reveal the genetic and neuronal basis underlying the sex-specific interaction between sleep and sexual behaviors in Drosophila, and provide insights into how competing behaviors are co-regulated.Genes and circuits involved in sleep and sexual arousal have been extensively studied in Drosophila. Here the authors identify the sex determination genes fruitless and doublesex, and a sex-specific P1-DN1 neuronal feedback that governs the interaction between these competing behaviors.

On their best behavior: how animal behavior can help determine the combined effects of species interactions and climate change.

PubMed

Harmon, Jason P; Barton, Brandon T

2013-09-01

The increasingly appreciated link between climate change and species interactions has the potential to help us understand and predict how organisms respond to a changing environment. As this connection grows, it becomes even more important to appreciate the mechanisms that create and control the combined effect of these factors. However, we believe one such important set of mechanisms comes from species' behavior and the subsequent trait-mediated interactions, as opposed to the more often studied density-mediated effects. Behavioral mechanisms are already well appreciated for mitigating the separate effects of the environment and species interactions. Thus, they could be at the forefront for understanding the combined effects. In this review, we (1) show some of the known behaviors that influence the individual and combined effects of climate change and species interactions; (2) conceptualize general ways behavior may mediate these combined effects; and (3) illustrate the potential importance of including behavior in our current tools for predicting climate change effects. In doing so, we hope to promote more research on behavior and other mechanistic factors that may increase our ability to accurately predict climate change effects. © 2013 New York Academy of Sciences.

How does tissue regeneration influence the mechanical behavior of additively manufactured porous biomaterials?

PubMed

Hedayati, R; Janbaz, S; Sadighi, M; Mohammadi-Aghdam, M; Zadpoor, A A

2017-01-01

Although the initial mechanical properties of additively manufactured porous biomaterials are intensively studied during the last few years, almost no information is available regarding the evolution of the mechanical properties of implant-bone complex as the tissue regeneration progresses. In this paper, we studied the effects of tissue regeneration on the static and fatigue behavior of selective laser melted porous titanium structures with three different porosities (i.e. 77, 81, and 85%). The porous structures were filled with four different polymeric materials with mechanical properties in the range of those observed for de novo bone (0.7GPa

Simplifying study of fever's dramatic relief of autistic behavior.

PubMed

Good, Peter

2017-02-01

Dramatic relief of autistic behavior by infectious fever continues to tantalize parents and practitioners, yet researchers still hesitate to study its physiology/biochemistry, fearing stress and heat of brain imaging, contagion, and fever's complexity. Yet what could be more revealing than a common event that virtually 'normalizes' autistic behavior for a time? This paper proposes study of three simplified scenarios: (1) improvements appearing hours before fever, (2) return of autistic behavior soon after fever, (3) improvements persisting long after fever. Each scenario limits some risk - and some explanation - inviting triangulation of decisive factor(s) in relief and recurrence. Return of autistic behavior after fever may be most revealing. The complex mechanisms that generated fever have all abated; simpler cooling mechanisms prevail - how many plausible explanations can there be? The decisive factor in fever's benefit is concluded to be water drawn/carried from brain myelin and astrocytes by osmolytes glutamine and taurine released from muscles and brain; the decisive factor in return of autistic behavior after fever is return of water. Copyright © 2016 European Society for Clinical Nutrition and Metabolism. Published by Elsevier Ltd. All rights reserved.

Low-temperature behavior of core-softened models: water and silica behavior.

PubMed

Jagla, E A

2001-06-01

A core-softened model of a glass forming fluid is numerically studied in the limit of very low temperatures. The model shows two qualitatively different behaviors depending on the strength of the attraction between particles. For no or low attraction, the changes of density as a function of pressure are smooth, although hysteretic due to mechanical metastabilities. For larger attraction, sudden changes of density upon compressing and decompressing occur. This global mechanical instability is correlated to the existence of a thermodynamic first-order amorphous-amorphous transition. The two different behaviors obtained correspond qualitatively to the different phenomenology observed in silica and water.

Representing Sex in the Brain, One Module at a Time

PubMed Central

Yang, Cindy F.; Shah, Nirao M.

2014-01-01

Summary Sexually dimorphic behaviors, qualitative or quantitative differences in behaviors between the sexes, result from the activity of a sexually differentiated nervous system. Sensory cues and sex hormones control the entire repertoire of sexually dimorphic behaviors, including those commonly thought to be charged with emotion such as courtship and aggression. Recent studies show that these over-arching control mechanisms regulate distinct genes and neurons that in turn specify the display of such behaviors in a modular manner. How such modular control is transformed into cohesive internal states that correspond to sexually dimorphic behavior is poorly understood. We summarize current understanding of the neural circuit control of sexually dimorphic behaviors from several perspectives, including how neural circuits in general, and sexually dimorphic neurons in particular, can generate sex differences in behavior, and how molecular mechanisms and evolutionary constraints shape these behaviors. We propose that emergent themes such as the modular genetic and neural control of dimorphic behavior are broadly applicable to the neural control of other behaviors. PMID:24742456

The mouse that roared: neural mechanisms of social hierarchy.

PubMed

Wang, Fei; Kessels, Helmut W; Hu, Hailan

2014-11-01

Hierarchical social status greatly influences behavior and health. Human and animal studies have begun to identify the brain regions that are activated during the formation of social hierarchies. They point towards the prefrontal cortex (PFC) as a central regulator, with brain areas upstream of the PFC conveying information about social status, and downstream brain regions executing dominance behavior. This review summarizes our current knowledge on the neural circuits that control social status. We discuss how the neural mechanisms for various types of dominance behavior can be studied in laboratory rodents by selective manipulation of neuronal activity or synaptic plasticity. These studies may help in finding the cause of social stress-related mental and physical health problems. Copyright © 2014 Elsevier Ltd. All rights reserved.

Spatiotemporal properties of microsaccades: Model predictions and experimental tests

NASA Astrophysics Data System (ADS)

Zhou, Jian-Fang; Yuan, Wu-Jie; Zhou, Zhao

2016-10-01

Microsaccades are involuntary and very small eye movements during fixation. Recently, the microsaccade-related neural dynamics have been extensively investigated both in experiments and by constructing neural network models. Experimentally, microsaccades also exhibit many behavioral properties. It’s well known that the behavior properties imply the underlying neural dynamical mechanisms, and so are determined by neural dynamics. The behavioral properties resulted from neural responses to microsaccades, however, are not yet understood and are rarely studied theoretically. Linking neural dynamics to behavior is one of the central goals of neuroscience. In this paper, we provide behavior predictions on spatiotemporal properties of microsaccades according to microsaccade-induced neural dynamics in a cascading network model, which includes both retinal adaptation and short-term depression (STD) at thalamocortical synapses. We also successfully give experimental tests in the statistical sense. Our results provide the first behavior description of microsaccades based on neural dynamics induced by behaving activity, and so firstly link neural dynamics to behavior of microsaccades. These results indicate strongly that the cascading adaptations play an important role in the study of microsaccades. Our work may be useful for further investigations of the microsaccadic behavioral properties and of the underlying neural dynamical mechanisms responsible for the behavioral properties.

Differential effects of ethanol on feline rage and predatory attack behavior: an underlying neural mechanism.

PubMed

Schubert, K; Shaikh, M B; Han, Y; Poherecky, L; Siegel, A

1996-08-01

Previous studies have shown that, at certain dose levels, ethanol can exert a powerful, facilitatory effect on aggressive behavior in both animals and humans. In the cat, however, it was discovered that ethanol differentially alters two forms of aggression that are common to this species. Defensive rage behavior is significantly enhanced, whereas predatory attack behavior is suppressed by ethanol administration. One possible mechanism governing alcohol's potentiation of defensive rage behavior is that it acts on the descending pathway from the medial hypothalamus to the midbrain periaqueductal gray (PAG)-an essential pathway for the expression of defensive rage behavior that uses excitatory amino acids as a neurotransmitter. This hypothesis is supported by the finding that the excitatory effects of alcohol on defensive rage behavior are blocked by administration of the N-methyl-D-aspartate antagonist alpha-2-amino-7-phosphoheptanoic acid (AP-7) when microinjected into the periaqueductal gray, a primary neuronal target of descending fibers from the medial hypothalamus that mediate the expression of defensive rage behavior. Thus, the present study establishes for the first time a specific component of the neural circuit for defensive rage behavior over which the potentiating effects of ethanol are mediated.

Numerical Study of the Complex Temporal Pattern of Spontaneous Oscillation in Bullfrog Saccular Hair Cells

NASA Astrophysics Data System (ADS)

Roongthumskul, Yuttana; Fredrickson-Hemsing, Lea; Kao, Albert; Bozovic, Dolores

2011-11-01

Hair bundles of the bullfrog sacculus display spontaneous oscillations that show complex temporal profiles. Quiescent intervals are typically interspersed with oscillations, analogous to bursting behavior observed in neural systems. By introducing slow calcium dynamics into the theoretical model of bundle mechanics, we reproduce numerically the multi-mode oscillations and explore the effects of internal parameters on the temporal profiles and the frequency tuning of their linear response functions. We also study the effects of mechanical overstimulation on the oscillatory behavior.

Frequent Nonprescription Stimulant Use and Risky Behaviors in College Students: The Role of Effortful Control

ERIC Educational Resources Information Center

Reid, Adam M.; Graziano, Paulo A.; Balkhi, Amanda M.; McNamara, Joseph P. H.; Cottler, Linda B.; Meneses, Evander; Geffken, Gary R.

2015-01-01

Objective: The goal of this study was to (a) investigate the association between nonprescription stimulant use (NPSU) and risky behaviors, including risky sex, driving, financial behaviors, and drug use and (b) collect preliminary evidence on mechanisms that may link NPSU to risky behaviors. Participants: A sample of 555 college students was…

Mechanism underlying the diverse collective behavior in the swarm oscillator model

NASA Astrophysics Data System (ADS)

Iwasa, Masatomo; Tanaka, Dan

2017-09-01

The swarm oscillator model describes the long-time behavior of interacting chemotactic particles, and it shows numerous types of macroscopic patterns. However, the reason why so many kinds of patterns emerge is not clear. In this study, we elucidate the mechanism underlying the diversity of the pattens by analyzing the model for two particles. Focusing on the behavior when the two particles are spatially close, we find that the dynamics is classified into eight types, which explain most of the observed 13 types of patterns.

Direct Observation of Markovian Behavior of the Mechanical Unfolding of Individual Proteins

PubMed Central

Cao, Yi; Kuske, Rachel; Li, Hongbin

2008-01-01

Single-molecule force-clamp spectroscopy is a valuable tool to analyze unfolding kinetics of proteins. Previous force-clamp spectroscopy experiments have demonstrated that the mechanical unfolding of ubiquitin deviates from the generally assumed Markovian behavior and involves the features of glassy dynamics. Here we use single molecule force-clamp spectroscopy to study the unfolding kinetics of a computationally designed fast-folding mutant of the small protein GB1, which shares a similar β-grasp fold as ubiquitin. By treating the mechanical unfolding of polyproteins as the superposition of multiple identical Poisson processes, we developed a simple stochastic analysis approach to analyze the dwell time distribution of individual unfolding events in polyprotein unfolding trajectories. Our results unambiguously demonstrate that the mechanical unfolding of NuG2 fulfills all criteria of a memoryless Markovian process. This result, in contrast with the complex mechanical unfolding behaviors observed for ubiquitin, serves as a direct experimental demonstration of the Markovian behavior for the mechanical unfolding of a protein and reveals the complexity of the unfolding dynamics among structurally similar proteins. Furthermore, we extended our method into a robust and efficient pseudo-dwell-time analysis method, which allows one to make full use of all the unfolding events obtained in force-clamp experiments without categorizing the unfolding events. This method enabled us to measure the key parameters characterizing the mechanical unfolding energy landscape of NuG2 with improved precision. We anticipate that the methods demonstrated here will find broad applications in single-molecule force-clamp spectroscopy studies for a wide range of proteins. PMID:18375518

Mechanical and Fatigue Properties of Additively Manufactured Metallic Materials

NASA Astrophysics Data System (ADS)

Yadollahi, Aref

This study aims to investigate the mechanical and fatigue behavior of additively manufactured metallic materials. Several challenges associated with different metal additive manufacturing (AM) techniques (i.e. laser-powder bed fusion and direct laser deposition) have been addressed experimentally and numerically. Experiments have been carried out to study the effects of process inter-layer time interval--i.e. either building the samples one-at-a-time or multi-at-a-time (in-parallel)--on the microstructural features and mechanical properties of 316L stainless steel samples, fabricated via a direct laser deposition (DLD). Next, the effect of building orientation--i.e. the orientation in which AM parts are built--on microstructure, tensile, and fatigue behaviors of 17-4 PH stainless steel, fabricated via a laser-powder bed fusion (L-PBF) method was investigated. Afterwards, the effect of surface finishing--here, as-built versus machined--on uniaxial fatigue behavior and failure mechanisms of Inconel 718 fabricated via a laser-powder bed fusion technique was sought. The numerical studies, as part of this dissertation, aimed to model the mechanical behavior of AM materials, under monotonic and cyclic loading, based on the observations and findings from the experiments. Despite significant research efforts for optimizing process parameters, achieving a homogenous, defect-free AM product--immediately after fabrication--has not yet been fully demonstrated. Thus, one solution for ensuring the adoption of AM materials for application should center on predicting the variations in mechanical behavior of AM parts based on their resultant microstructure. In this regard, an internal state variable (ISV) plasticity-damage model was employed to quantify the damage evolution in DLD 316L SS, under tensile loading, using the microstructural features associated with the manufacturing process. Finally, fatigue behavior of AM parts has been modeled based on the crack-growth concept. Using the FASTRAN code, the fatigue-life of L-PBF Inconel 718 was accurately calculated using the size and shape of process-induced voids in the material. In addition, the maximum valley depth of the surface profile was found to be an appropriate representative of the initial surface flaw for fatigue-life prediction of AM materials in an as-built surface condition.

Caenorhabditis elegans as a Model to Study the Molecular and Genetic Mechanisms of Drug Addiction

PubMed Central

Engleman, Eric A.; Katner, Simon N.; Neal-Beliveau, Bethany S.

2016-01-01

Drug addiction takes a massive toll on society. Novel animal models are needed to test new treatments and understand the basic mechanisms underlying addiction. Rodent models have identified the neurocircuitry involved in addictive behavior and indicate that rodents possess some of the same neurobiologic mechanisms that mediate addiction in humans. Recent studies indicate that addiction is mechanistically and phylogenetically ancient and many mechanisms that underlie human addiction are also present in invertebrates. The nematode Caenorhabditis elegans has conserved neurobiologic systems with powerful molecular and genetic tools and a rapid rate of development that enables cost-effective translational discovery. Emerging evidence suggests that C. elegans is an excellent model to identify molecular mechanisms that mediate drug-induced behavior and potential targets for medications development for various addictive compounds. C. elegans emit many behaviors that can be easily quantitated including some that involve interactions with the environment. Ethanol (EtOH) is the best-studied drug-of-abuse in C. elegans and at least 50 different genes/targets have been identified as mediating EtOH’s effects and polymorphisms in some orthologs in humans are associated with alcohol use disorders. C. elegans has also been shown to display dopamine and cholinergic system–dependent attraction to nicotine and demonstrate preference for cues previously associated with nicotine. Cocaine and methamphetamine have been found to produce dopamine-dependent reward-like behaviors in C. elegans. These behavioral tests in combination with genetic/molecular manipulations have led to the identification of dozens of target genes/systems in C. elegans that mediate drug effects. The one target/gene identified as essential for drug-induced behavioral responses across all drugs of abuse was the cat-2 gene coding for tyrosine hydroxylase, which is consistent with the role of dopamine neurotransmission in human addiction. Overall, C. elegans can be used to model aspects of drug addiction and identify systems and molecular mechanisms that mediate drug effects. The findings are surprisingly consistent with analogous findings in higher-level organisms. Further, model refinement is warranted to improve model validity and increase utility for medications development. PMID:26810004

Caenorhabditis elegans as a Model to Study the Molecular and Genetic Mechanisms of Drug Addiction.

PubMed

Engleman, Eric A; Katner, Simon N; Neal-Beliveau, Bethany S

2016-01-01

Drug addiction takes a massive toll on society. Novel animal models are needed to test new treatments and understand the basic mechanisms underlying addiction. Rodent models have identified the neurocircuitry involved in addictive behavior and indicate that rodents possess some of the same neurobiologic mechanisms that mediate addiction in humans. Recent studies indicate that addiction is mechanistically and phylogenetically ancient and many mechanisms that underlie human addiction are also present in invertebrates. The nematode Caenorhabditis elegans has conserved neurobiologic systems with powerful molecular and genetic tools and a rapid rate of development that enables cost-effective translational discovery. Emerging evidence suggests that C. elegans is an excellent model to identify molecular mechanisms that mediate drug-induced behavior and potential targets for medications development for various addictive compounds. C. elegans emit many behaviors that can be easily quantitated including some that involve interactions with the environment. Ethanol (EtOH) is the best-studied drug-of-abuse in C. elegans and at least 50 different genes/targets have been identified as mediating EtOH's effects and polymorphisms in some orthologs in humans are associated with alcohol use disorders. C. elegans has also been shown to display dopamine and cholinergic system-dependent attraction to nicotine and demonstrate preference for cues previously associated with nicotine. Cocaine and methamphetamine have been found to produce dopamine-dependent reward-like behaviors in C. elegans. These behavioral tests in combination with genetic/molecular manipulations have led to the identification of dozens of target genes/systems in C. elegans that mediate drug effects. The one target/gene identified as essential for drug-induced behavioral responses across all drugs of abuse was the cat-2 gene coding for tyrosine hydroxylase, which is consistent with the role of dopamine neurotransmission in human addiction. Overall, C. elegans can be used to model aspects of drug addiction and identify systems and molecular mechanisms that mediate drug effects. The findings are surprisingly consistent with analogous findings in higher-level organisms. Further, model refinement is warranted to improve model validity and increase utility for medications development. Copyright © 2016. Published by Elsevier Inc.

Dimensions of Peer Influences and Their Relationship to Adolescents' Aggression, Other Problem Behaviors and Prosocial Behavior.

PubMed

Farrell, Albert D; Thompson, Erin L; Mehari, Krista R

2017-06-01

Although peers are a major influence during adolescence, the relative importance of specific mechanisms of peer influence on the development of problem behavior is not well understood. This study investigated five domains of peer influence and their relationships to adolescents' problem and prosocial behaviors. Self-report and teacher ratings were obtained for 1787 (53 % female) urban middle school students. Peer pressure for fighting and friends' delinquent behavior were uniquely associated with aggression, drug use and delinquent behavior. Friends' prosocial behavior was uniquely associated with prosocial behavior. Friends' support for fighting and friends' support for nonviolence were not as clearly related to behavior. Findings were generally consistent across gender. This study highlights the importance of studying multiple aspects of peer influences on adolescents' behavior.

Differential gene expression associated with honey bee grooming behavior in response to varroa mites

USDA-ARS?s Scientific Manuscript database

Honey bee (Apis mellifera) grooming behavior is an important mechanism of resistance against the parasitic mite Varroa destructor. This research was conducted to study associations between grooming behavior and the expression of selected immune, neural, detoxification, developmental and health-relat...

Emotion Dysregulation and Risky Sexual Behavior in Revictimization

ERIC Educational Resources Information Center

Messman-Moore, Terri L.; Walsh, Kate L.; DiLillo, David

2010-01-01

Objective: The current study examined emotion dysregulation as a mechanism underlying risky sexual behavior and sexual revictimization among adult victims of child sexual abuse (CSA) and child physical abuse (CPA). Methods: Participants were 752 college women. Victimization history, emotion dysregulation, and risky sexual behavior were assessed…

Shoaling develops with age in Zebrafish (Danio rerio)

PubMed Central

Buske, Christine; Gerlai, Robert

2010-01-01

The biological mechanisms of human social behavior are complex. Animal models may facilitate the understanding of these mechanisms and may help one to develop treatment strategies for abnormal human social behavior, a core symptom in numerous clinical conditions. The zebrafish is perhaps the most social vertebrate among commonly used laboratory species. Given its practical features and the numerous genetic tools developed for it, it should be a promising tool. Zebrafish shoal, i.e. form tight multimember groups, but the ontogenesis of this behavior has not been described. Analyzing the development of shoaling is a step towards discovering the mechanisms of this behavior. Here we study age-dependent changes of shoaling in zebrafish from day 7 post fertilization to over 5 months of age by measuring the distance between all pairs of fish in freely swimming groups of ten subjects. Our longitudinal (repeated measure within subject) and cross sectional (non-repeated measure between subject) analyses both demonstrated a significant increase of shoaling with age (decreased distance between shoal members). Given the sophisticated genetic and developmental biology methods already available for zebrafish, we argue that our behavioral results open a new avenue towards the understanding of the development of vertebrate social behavior and of its mechanisms and abnormalities. PMID:20837077

The effect of storage temperature on blue cheese mechanical properties.

PubMed

Joyner Melito, Helen S; Francis, Dorothy; Luzzi, Brooke; Johnson, John R

2018-06-01

Blue cheese is commonly aged for 60 days at 10°C after curing. However, some manufacturers store blue cheese at 4°C and the effect of lower storage temperature on blue cheese final properties is unknown. Thus, the objective of this study was to determine the effect of storage temperature and time on blue cheese mechanical behaviors. Blue cheeses were stored at 4 or 10°C for 77 days after production. Composition and small- and large-strain rheological behaviors were evaluated every 2 weeks of storage. Storage time had significant impact on blue cheese rheological behaviors; storage temperature did not. Large-strain compressive force and viscoelastic moduli decreased with storage time, and the extent of nonlinear viscoelastic behavior increased. These results indicated that sample microstructure likely weakened and was more easily deformed as storage time increased. Overall, blue cheese can be stored at 4-10°C without significant changes to its composition or mechanical behavior. The results of this work can be used by blue cheese manufacturers to better understand the impact of storage time and temperature on blue cheese end quality. Manufacturers can take advantage of the effects of storage time on blue cheese mechanical behaviors to determine how long to age blue cheese to achieve the desired texture. © 2017 Wiley Periodicals, Inc.

Dynamic behavior of the mechanical systems from the structure of a hybrid automobile

NASA Astrophysics Data System (ADS)

Dinel, Popa; Irina, Tudor; Nicolae-Doru, Stănescu

2017-10-01

In introduction are presented solutions of planetary mechanisms that can be used in the construction of the hybrid automobiles where the thermal and electrical sources must be coupled. The systems have in their composition a planetary mechanism with two degrees of mobility at which are coupled a thermal engine, two revertible electrical machines, a gear transmission with four gears and a differential mechanism which transmits the motion at the driving wheels. For the study of the dynamical behavior, with numerical results, one designs such mechanisms, models the elements with solids in AutoCAD, and obtains the mechanical properties of the elements. Further on, we present and solve the equations of motion of a hybrid automotive for which one knows the dynamical parameters.

Sleep-Related Safety Behaviors and Dysfunctional Beliefs Mediate the Efficacy of Online CBT for Insomnia: A Randomized Controlled Trial.

PubMed

Lancee, Jaap; Eisma, Maarten C; van Straten, Annemieke; Kamphuis, Jan H

2015-01-01

Several trials have demonstrated the efficacy of online cognitive behavioral therapy (CBT) for insomnia. However, few studies have examined putative mechanisms of change based on the cognitive model of insomnia. Identification of modifiable mechanisms by which the treatment works may guide efforts to further improve the efficacy of insomnia treatment. The current study therefore has two aims: (1) to replicate the finding that online CBT is effective for insomnia and (2) to test putative mechanism of change (i.e., safety behaviors and dysfunctional beliefs). Accordingly, we conducted a randomized controlled trial in which individuals with insomnia were randomized to either online CBT for insomnia (n = 36) or a waiting-list control group (n = 27). Baseline and posttest assessments included questionnaires assessing insomnia severity, safety behaviors, dysfunctional beliefs, anxiety and depression, and a sleep diary. Three- and six-month assessments were administered to the CBT group only. Results show moderate to large statistically significant effects of the online treatment compared to the waiting list on insomnia severity, sleep measures, sleep safety behaviors, and dysfunctional beliefs. Furthermore, dysfunctional beliefs and safety behaviors mediated the effects of treatment on insomnia severity and sleep efficiency. Together, these findings corroborate the efficacy of online CBT for insomnia, and suggest that these effects were produced by changing maladaptive beliefs, as well as safety behaviors. Treatment protocols for insomnia may specifically be enhanced by more focused attention on the comprehensive fading of sleep safety behaviors, for instance through behavioral experiments.

Mechanics of additively manufactured biomaterials.

PubMed

Zadpoor, Amir A

2017-06-01

Additive manufacturing (3D printing) has found many applications in healthcare including fabrication of biomaterials as well as bioprinting of tissues and organs. Additively manufactured (AM) biomaterials may possess arbitrarily complex micro-architectures that give rise to novel mechanical, physical, and biological properties. The mechanical behavior of such porous biomaterials including their quasi-static mechanical properties and fatigue resistance is not yet well understood. It is particularly important to understand the relationship between the designed micro-architecture (topology) and the resulting mechanical properties. The current special issue is dedicated to understanding the mechanical behavior of AM biomaterials. Although various types of AM biomaterials are represented in the special issue, the primary focus is on AM porous metallic biomaterials. As a prelude to this special issue, this editorial reviews some of the latest findings in the mechanical behavior of AM porous metallic biomaterials so as to describe the current state-of-the-art and set the stage for the other studies appearing in the issue. Some areas that are important for future research are also briefly mentioned. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nonlinear Inelastic Mechanical Behavior Of Epoxy Resin Polymeric Materials

NASA Astrophysics Data System (ADS)

Yekani Fard, Masoud

Polymer and polymer matrix composites (PMCs) materials are being used extensively in different civil and mechanical engineering applications. The behavior of the epoxy resin polymers under different types of loading conditions has to be understood before the mechanical behavior of Polymer Matrix Composites (PMCs) can be accurately predicted. In many structural applications, PMC structures are subjected to large flexural loadings, examples include repair of structures against earthquake and engine fan cases. Therefore it is important to characterize and model the flexural mechanical behavior of epoxy resin materials. In this thesis, a comprehensive research effort was undertaken combining experiments and theoretical modeling to investigate the mechanical behavior of epoxy resins subject to different loading conditions. Epoxy resin E 863 was tested at different strain rates. Samples with dog-bone geometry were used in the tension tests. Small sized cubic, prismatic, and cylindrical samples were used in compression tests. Flexural tests were conducted on samples with different sizes and loading conditions. Strains were measured using the digital image correlation (DIC) technique, extensometers, strain gauges, and actuators. Effects of triaxiality state of stress were studied. Cubic, prismatic, and cylindrical compression samples undergo stress drop at yield, but it was found that only cubic samples experience strain hardening before failure. Characteristic points of tensile and compressive stress strain relation and load deflection curve in flexure were measured and their variations with strain rate studied. Two different stress strain models were used to investigate the effect of out-of-plane loading on the uniaxial stress strain response of the epoxy resin material. The first model is a strain softening with plastic flow for tension and compression. The influence of softening localization on material behavior was investigated using the DIC system. It was found that compression plastic flow has negligible influence on flexural behavior in epoxy resins, which are stronger in pre-peak and post-peak softening in compression than in tension. The second model was a piecewise-linear stress strain curve simplified in the post-peak response. Beams and plates with different boundary conditions were tested and analytically studied. The flexural over-strength factor for epoxy resin polymeric materials were also evaluated.

An investigation of concentrated and distributed strain inducing constraints for training shape memory alloys

NASA Astrophysics Data System (ADS)

Parent, Pauline Marie

Borderline personality disorder (BPD) is a severe mental illness characterized by high rates of engagement in distress-induced risk behavior. Unfortunately, extant laboratory-based risk paradigms have failed to account for the role of distress in precipitating risk behavior, so many questions remain about processes mechanisms that underlie this behavior. The current study examined affect as a moderator of the relationship between diagnostic status and risk behavior, as measured by a behavioral risk task, and affective and non-affective neurocognitive functioning as potential mediators of this relationship. Results indicated that individuals with BPD engaged in more risk behavior in the distress condition than in the neutral condition, whereas individuals without BPD showed a decrease in risk behavior across the two conditions. However, corresponding changes in executive functioning were not observed, suggesting the need for continued research to identify alternative mechanisms (e.g., neurocognitive, motivational) to explain this effect.

A Positive Affective Neuroendocrinology Approach to Reward and Behavioral Dysregulation

PubMed Central

Welker, Keith M.; Gruber, June; Mehta, Pranjal H.

2015-01-01

Emerging lines of research suggest that both testosterone and maladaptive reward processing can modulate behavioral dysregulation. Yet, to date, no integrative account has been provided that systematically explains neuroendocrine function, dysregulation of reward, and behavioral dysregulation in a unified perspective. This is particularly important given specific neuroendocrine systems are potential mechanisms underlying and giving rise to reward-relevant behaviors. In this review, we propose a forward-thinking approach to study the mechanisms of reward and behavioral dysregulation from a positive affective neuroendocrinology (PANE) perspective. This approach holds that testosterone increases reward processing and motivation, which increase the likelihood of behavioral dysregulation. Additionally, the PANE framework holds that reward processing mediates the effects of testosterone on behavioral dysregulation. We also explore sources of potential sex differences and the roles of age, cortisol, and individual differences within the PANE framework. Finally, we discuss future prospects for research questions and methodology in the emerging field of affective neuroendocrinology. PMID:26191007

Therapeutic Effects of Extinction Learning as a Model of Exposure Therapy in Rats.

PubMed

Fucich, Elizabeth A; Paredes, Denisse; Morilak, David A

2016-12-01

Current treatments for stress-related psychiatric disorders, such as depression and posttraumatic stress disorder (PTSD), are inadequate. Cognitive behavioral psychotherapies, including exposure therapy, are an alternative to pharmacotherapy, but the neurobiological mechanisms are unknown. Preclinical models demonstrating therapeutic effects of behavioral interventions are required to investigate such mechanisms. Exposure therapy bears similarity to extinction learning. Thus, we investigated the therapeutic effects of extinction learning as a behavioral intervention to model exposure therapy in rats, testing its effectiveness in reversing chronic stress-induced deficits in cognitive flexibility and coping behavior that resemble dimensions of depression and PTSD. Rats were fear-conditioned by pairing a tone with footshock, and then exposed to chronic unpredictable stress (CUS) that induces deficits in cognitive set-shifting and active coping behavior. They then received an extinction learning session as a therapeutic intervention by repeated exposure to the tone with no shock. Effects on cognitive flexibility and coping behavior were assessed 24 h later on the attentional set-shifting test or shock-probe defensive burying test, respectively. Extinction reversed the CUS-induced deficits in cognitive flexibility and coping behavior, and increased phosphorylation of ribosomal protein S6 in the medial prefrontal cortex (mPFC) of stress-compromised rats, suggesting a role for activity-dependent protein synthesis in the therapeutic effect. Inhibiting protein synthesis by microinjecting anisomycin into mPFC blocked the therapeutic effect of extinction on cognitive flexibility. These results demonstrate the utility of extinction as a model by which to study mechanisms underlying exposure therapy, and suggest these mechanisms involve protein synthesis in the mPFC, the further study of which may identify novel therapeutic targets.

Therapeutic Effects of Extinction Learning as a Model of Exposure Therapy in Rats

PubMed Central

Fucich, Elizabeth A; Paredes, Denisse; Morilak, David A

2016-01-01

Current treatments for stress-related psychiatric disorders, such as depression and posttraumatic stress disorder (PTSD), are inadequate. Cognitive behavioral psychotherapies, including exposure therapy, are an alternative to pharmacotherapy, but the neurobiological mechanisms are unknown. Preclinical models demonstrating therapeutic effects of behavioral interventions are required to investigate such mechanisms. Exposure therapy bears similarity to extinction learning. Thus, we investigated the therapeutic effects of extinction learning as a behavioral intervention to model exposure therapy in rats, testing its effectiveness in reversing chronic stress-induced deficits in cognitive flexibility and coping behavior that resemble dimensions of depression and PTSD. Rats were fear-conditioned by pairing a tone with footshock, and then exposed to chronic unpredictable stress (CUS) that induces deficits in cognitive set-shifting and active coping behavior. They then received an extinction learning session as a therapeutic intervention by repeated exposure to the tone with no shock. Effects on cognitive flexibility and coping behavior were assessed 24 h later on the attentional set-shifting test or shock-probe defensive burying test, respectively. Extinction reversed the CUS-induced deficits in cognitive flexibility and coping behavior, and increased phosphorylation of ribosomal protein S6 in the medial prefrontal cortex (mPFC) of stress-compromised rats, suggesting a role for activity-dependent protein synthesis in the therapeutic effect. Inhibiting protein synthesis by microinjecting anisomycin into mPFC blocked the therapeutic effect of extinction on cognitive flexibility. These results demonstrate the utility of extinction as a model by which to study mechanisms underlying exposure therapy, and suggest these mechanisms involve protein synthesis in the mPFC, the further study of which may identify novel therapeutic targets. PMID:27417516

Tendon exhibits complex poroelastic behavior at the nanoscale as revealed by high-frequency AFM-based rheology.

PubMed

Connizzo, Brianne K; Grodzinsky, Alan J

2017-03-21

Tendons transmit load from muscle to bone by utilizing their unique static and viscoelastic tensile properties. These properties are highly dependent on the composition and structure of the tissue matrix, including the collagen I hierarchy, proteoglycans, and water. While the role of matrix constituents in the tensile response has been studied, their role in compression, particularly in matrix pressurization via regulation of fluid flow, is not well understood. Injured or diseased tendons and tendon regions that naturally experience compression are known to have alterations in glycosaminoglycan content, which could modulate fluid flow and ultimately mechanical function. While recent theoretical studies have predicted tendon mechanics using poroelastic theory, no experimental data have directly demonstrated such behavior. In this study, we use high-bandwidth AFM-based rheology to determine the dynamic response of tendons to compressive loading at the nanoscale and to determine the presence of poroelastic behavior. Tendons are found to have significant characteristic dynamic relaxation behavior occurring at both low and high frequencies. Classic poroelastic behavior is observed, although we hypothesize that the full dynamic response is caused by a combination of flow-dependent poroelasticity as well as flow-independent viscoelasticity. Tendons also demonstrate regional dependence in their dynamic response, particularly near the junction of tendon and bone, suggesting that the structural and compositional heterogeneity in tendon may be responsible for regional poroelastic behavior. Overall, these experiments provide the foundation for understanding fluid-flow-dependent poroelastic mechanics of tendon, and the methodology is valuable for assessing changes in tendon matrix compressive behavior at the nanoscale. Copyright © 2017 Elsevier Ltd. All rights reserved.

Cell-matrix mechanical interaction in electrospun polymeric scaffolds for tissue engineering: Implications for scaffold design and performance.

PubMed

Kennedy, Kelsey M; Bhaw-Luximon, Archana; Jhurry, Dhanjay

2017-03-01

Engineered scaffolds produced by electrospinning of biodegradable polymers offer a 3D, nanofibrous environment with controllable structural, chemical, and mechanical properties that mimic the extracellular matrix of native tissues and have shown promise for a number of tissue engineering applications. The microscale mechanical interactions between cells and electrospun matrices drive cell behaviors including migration and differentiation that are critical to promote tissue regeneration. Recent developments in understanding these mechanical interactions in electrospun environments are reviewed, with emphasis on how fiber geometry and polymer structure impact on the local mechanical properties of scaffolds, how altering the micromechanics cues cell behaviors, and how, in turn, cellular and extrinsic forces exerted on the matrix mechanically remodel an electrospun scaffold throughout tissue development. Techniques used to measure and visualize these mechanical interactions are described. We provide a critical outlook on technological gaps that must be overcome to advance the ability to design, assess, and manipulate the mechanical environment in electrospun scaffolds toward constructs that may be successfully applied in tissue engineering and regenerative medicine. Tissue engineering requires design of scaffolds that interact with cells to promote tissue development. Electrospinning is a promising technique for fabricating fibrous, biomimetic scaffolds. Effects of electrospun matrix microstructure and biochemical properties on cell behavior have been extensively reviewed previously; here, we consider cell-matrix interaction from a mechanical perspective. Micromechanical properties as a driver of cell behavior has been well established in planar substrates, but more recently, many studies have provided new insights into mechanical interaction in fibrillar, electrospun environments. This review provides readers with an overview of how electrospun scaffold mechanics and cell behavior work in a dynamic feedback loop to drive tissue development, and discusses opportunities for improved design of mechanical environments that are conducive to tissue development. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Relationship between tendon stiffness and failure: a metaanalysis

PubMed Central

LaCroix, Andrew S.; Duenwald-Kuehl, Sarah E.; Lakes, Roderic S.

2013-01-01

Tendon is a highly specialized, hierarchical tissue designed to transfer forces from muscle to bone; complex viscoelastic and anisotropic behaviors have been extensively characterized for specific subsets of tendons. Reported mechanical data consistently show a pseudoelastic, stress-vs.-strain behavior with a linear slope after an initial toe region. Many studies report a linear, elastic modulus, or Young's modulus (hereafter called elastic modulus) and ultimate stress for their tendon specimens. Individually, these studies are unable to provide a broader, interstudy understanding of tendon mechanical behavior. Herein we present a metaanalysis of pooled mechanical data from a representative sample of tendons from different species. These data include healthy tendons and those altered by injury and healing, genetic modification, allograft preparation, mechanical environment, and age. Fifty studies were selected and analyzed. Despite a wide range of mechanical properties between and within species, elastic modulus and ultimate stress are highly correlated (R2 = 0.785), suggesting that tendon failure is highly strain-dependent. Furthermore, this relationship was observed to be predictable over controlled ranges of elastic moduli, as would be typical of any individual species. With the knowledge gained through this metaanalysis, noninvasive tools could measure elastic modulus in vivo and reasonably predict ultimate stress (or structural compromise) for diseased or injured tendon. PMID:23599401

Behavioral and Functional Assays for Investigating Mechanisms of Noxious Cold Detection and Multimodal Sensory Processing in Drosophila Larvae

PubMed Central

Patel, Atit A.; Cox, Daniel N.

2017-01-01

To investigate cellular, molecular and behavioral mechanisms of noxious cold detection, we developed cold plate behavioral assays and quantitative means for evaluating the predominant noxious cold-evoked contraction behavior. To characterize neural activity in response to noxious cold, we implemented a GCaMP6-based calcium imaging assay enabling in vivo studies of intracellular calcium dynamics in intact Drosophila larvae. We identified Drosophila class III multidendritic (md) sensory neurons as multimodal sensors of innocuous mechanical and noxious cold stimuli and to dissect the mechanistic bases of multimodal sensory processing we developed two independent functional assays. First, we developed an optogenetic dose response assay to assess whether levels of neural activation contributes to the multimodal aspects of cold sensitive sensory neurons. Second, we utilized CaMPARI, a photo-switchable calcium integrator that stably converts fluorescence from green to red in presence of high intracellular calcium and photo-converting light, to assess in vivo functional differences in neural activation levels between innocuous mechanical and noxious cold stimuli. These novel assays enable investigations of behavioral and functional roles of peripheral sensory neurons and multimodal sensory processing in Drosophila larvae. PMID:28835907

Nociception, pain, negative moods and behavior selection

PubMed Central

Baliki, Marwan N.; Apkarian, A. Vania

2015-01-01

Recent neuroimaging studies suggest that the brain adapts with pain, as well as imparts risk for developing chronic pain. Within this context we revisit the concepts for nociception, acute and chronic pain, and negative moods relative to behavior selection. We redefine nociception as the mechanism protecting the organism from injury; while acute pain as failure of avoidant behavior; and a mesolimbic threshold process that gates the transformation of nociceptive activity to conscious pain. Adaptations in this threshold process are envisioned to be critical for development of chronic pain. We deconstruct chronic pain into four distinct phases, each with specific mechanisms; and outline current state of knowledge regarding these mechanisms: The limbic brain imparting risk, while mesolimbic learning processes reorganizing the neocortex into a chronic pain state. Moreover, pain and negative moods are envisioned as a continuum of aversive behavioral learning, which enhance survival by protecting against threats. PMID:26247858

Better exercise adherence after treatment for cancer (BEAT Cancer) study: Rationale, design, and methods

PubMed Central

Rogers, Laura Q.; McAuley, Edward; Anton, Philip M.; Courneya, Kerry S.; Vicari, Sandra; Hopkins-Price, Patricia; Verhulst, Steven; Mocharnuk, Robert; Hoelzer, Karen

2011-01-01

Most breast cancer survivors do not engage in regular physical activity. Our physical activity behavior change intervention for breast cancer survivors significantly improved physical activity and health outcomes post-intervention during a pilot, feasibility study. Testing in additional sites with a larger sample and longer follow-up is warranted to confirm program effectiveness short and longer term. Importantly, the pilot intervention resulted in changes in physical activity and social cognitive theory constructs, enhancing our potential for testing mechanisms mediating physical activity behavior change. Here, we report the rationale, design, and methods for a two-site, randomized controlled trial comparing the effects of the BEAT Cancer physical activity behavior change intervention to usual care on short and longer term physical activity adherence among breast cancer survivors. Secondary aims include examining social cognitive theory mechanisms of physical activity behavior change and health benefits of the intervention. Study recruitment goal is 256 breast cancer survivors with a history of ductal carcinoma in situ or Stage I, II, or IIIA disease who have completed primary cancer treatment. Outcome measures are obtained at baseline, 3 months (i.e., immediately post-intervention), 6 months, and 12 months and include physical activity, psychosocial factors, fatigue, sleep quality, lower extremity joint dysfunction, cardiorespiratory fitness, muscle strength, and waist-to-hip ratio. Confirming behavior change effectiveness, health effects, and underlying mechanisms of physical activity behavior change interventions will facilitate translation to community settings for improving the health and well-being of breast cancer survivors. PMID:21983625

Can Molecular Hippocampal Alterations Explain Behavioral Differences in Prenatally Stressed Rats?

EPA Science Inventory

Studies in both humans and animals have shown that prenatal stress can alter cognitive function and other neurological behaviors in adult offspring. One possible underlying mechanism for this may lie with alterations in hippocampal gene expression. The present study examined geno...

Partner Influence in Diet and Exercise Behaviors: Testing Behavior Modeling, Social Control, and Normative Body Size.

PubMed

Perry, Brea; Ciciurkaite, Gabriele; Brady, Christy Freadreacea; Garcia, Justin

2016-01-01

Previous research has documented social contagion in obesity and related health behaviors, but less is known about the social processes underlying these patterns. Focusing on married or cohabitating couples, we simultaneously explore three potential social mechanisms influencing obesity: normative body size, social control, and behavior modeling. We analyze the association between partner characteristics and the obesity-related health behaviors of focal respondents, comparing the effects of partners' body type, partners' attempts to manage respondents' eating behaviors, and partners' own health behaviors on respondents' health behaviors (physical activity, fruit and vegetable consumption, and fast food consumption). Data on 215 partners are extracted from a larger study of social mechanisms of obesity in family and community contexts conducted in 2011 in the United States. Negative binomial regression models indicate that partner behavior is significantly related to respondent behavior (p < .001), net of controls. These results are suggestive of a behavior modeling mechanism in obesity-related patterns of consumption and physical activity. In contrast, we find little support for the influence of normative body size or partner social control in this sample, though generalizations about the relevance of these processes may be inappropriate. These results underscore the importance of policies and interventions that target dyads and social groups, suggesting that adoption of exercise or diet modifications in one individual is likely to spread to others, creating a social environment characterized by mutual reinforcement of healthy behavior.

Study on the behavior and mechanism of polycarbonate with hot-water aging

NASA Astrophysics Data System (ADS)

Kong, L. P.; Zhao, Y. X.; Zhou, C. H.; Huang, Y. H.; Tang, M.; Gao, J. G.

2016-07-01

The present work was concerned with hot-water aging behavior and mechanism of Bisphenol A polycarbonate (PC) used as food and packaging materials. It indicated that with the aging time prolonged, PC sample had internal defects and the mechanical properties of PC materials changed not too much, molecular weight decreased, thermal stability declined. Phenolic hydroxyl absorption intensity enhanced in IR spectra and the maximum absorption wavelength red shift of benzene in UV-Vis spectra, the level of BPA increased. The color change of PC sample was not apparent.

Limbic system seizures and aggressive behavior (superkindling effects).

PubMed

Andy, O J; Velamati, S

1978-01-01

This study was done to further analyze the neural mechanisms underlying aggressive behavior associated with psychomotor or temporal lobe seizures. The studies revealed that superkindling the aggressive system by sequential stimulations at seizure-inducing thresholds, of two or more sites in the limbic, hypothalamic, and basal ganglia structures facilitated the production of aggressive seizures. Aggressive behavior in the freely moving cat was evaluated in relation to the occurrence of hissing and growling during stimulation, after-discharge and postictal period. The behavior was correlated with the frequency of the elicited seizures and the seizure durations. Aggression did develop as a component behavioral manifestation of the limbic (psychomotor) seizure. Development of aggressive seizures was facilitated by "priming" the aggressive system. Optimum levels of aggressive behavior occurred with seizures of medium duration. Catecholamine blockers tended to attentuate the occurrence of aggression, whereas the agonist tended to facilitate it. Once the aggressive system was rendered hyperexcitable, exteroceptive stimuli also evoked aggressive attack behavior. It was concluded that repeatedly recurring limbic system seizures through superkindling mechanisms can eventually render the limbic-basal ganglia-preoptico-hypothalamic aggressive system hyper-responsive to both recurring seizures and to exteroceptive stimuli with resulting aggressive behavior with or without an accompanying seizure.

Controlling Surface Chemistry to Deconvolute Corrosion Benefits Derived from SMAT Processing

NASA Astrophysics Data System (ADS)

Murdoch, Heather A.; Labukas, Joseph P.; Roberts, Anthony J.; Darling, Kristopher A.

2017-07-01

Grain refinement through surface plastic deformation processes such as surface mechanical attrition treatment has shown measureable benefits for mechanical properties, but the impact on corrosion behavior has been inconsistent. Many factors obfuscate the particular corrosion mechanisms at work, including grain size, but also texture, processing contamination, and surface roughness. Many studies attempting to link corrosion and grain size have not been able to decouple these effects. Here we introduce a preprocessing step to mitigate the surface contamination effects that have been a concern in previous corrosion studies on plastically deformed surfaces; this allows comparison of corrosion behavior across grain sizes while controlling for texture and surface roughness. Potentiodynamic polarization in aqueous NaCl solution suggests that different corrosion mechanisms are responsible for samples prepared with the preprocessing step.

Plug Load Behavioral Change Demonstration Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Metzger, I.; Kandt, A.; VanGeet, O.

2011-08-01

This report documents the methods and results of a plug load study of the Environmental Protection Agency's Region 8 Headquarters in Denver, Colorado, conducted by the National Renewable Energy Laboratory. The study quantified the effect of mechanical and behavioral change approaches on plug load energy reduction and identified effective ways to reduce plug load energy. Load reduction approaches included automated energy management systems and behavioral change strategies.

Beyond general behavioral theories: structural discrepancy in young motorcyclist's risky driving behavior and its policy implications.

PubMed

Chung, Yi-Shih; Wong, Jinn-Tsai

2012-11-01

While many studies examine the mean score differences of psychological determinants between heterogeneous driver groups, this study reveals a structural discrepancy in a causal behavioral framework. Using young motorcyclists (ages 18-28) as subjects, this study investigates the various roles of key influential factors in determining risky driving behavior. Multi-group analysis of structural equation modeling shows that age and gender are two factors that can effectively distinguish heterogeneous driver groups exhibiting different decision-making mechanisms in shaping their risky driving behaviors. When encountering undesirable traffic conditions, road rage can immediately increase male motorcyclists' intentions to engage in risky driving behaviors; on the other hand, young female motorcyclists further calculate their perceived risk to determine whether to engage in risky driving behaviors. This result shows that there is a significant link between risk perception and traffic condition awareness for experienced drivers (ages 25-28), but not for younger drivers (ages 18-24). This finding shows that while well-developed theories such as planned behavior and risk homeostasis provide general frameworks to explain risky driving behavior, heterogeneous driver groups may exhibit structural discrepancies that reflect their various decision-making mechanisms. This suggests that, in addition to mean differences, understanding structural discrepancies among heterogeneous groups could help researchers identify effective intervention strategies. Copyright © 2011 Elsevier Ltd. All rights reserved.

Formulation and validation of a reduced order model of 2D materials exhibiting a two-phase microstructure as applied to graphene oxide

NASA Astrophysics Data System (ADS)

Benedetti, Ivano; Nguyen, Hoang; Soler-Crespo, Rafael A.; Gao, Wei; Mao, Lily; Ghasemi, Arman; Wen, Jianguo; Nguyen, SonBinh; Espinosa, Horacio D.

2018-03-01

Novel 2D materials, e.g., graphene oxide (GO), are attractive building blocks in the design of advanced materials due to their reactive chemistry, which can enhance interfacial interactions while providing good in-plane mechanical properties. Recent studies have hypothesized that the randomly distributed two-phase microstructure of GO, which arises due to its oxidized chemistry, leads to differences in nano- vs meso-scale mechanical responses. However, this effect has not been carefully studied using molecular dynamics due to computational limitations. Herein, a continuum mechanics model, formulated based on density functional based tight binding (DFTB) constitutive results for GO nano-flakes, is establish for capturing the effect of oxidation patterns on the material mechanical properties. GO is idealized as a continuum heterogeneous two-phase material, where the mechanical response of each phase, graphitic and oxidized, is informed from DFTB simulations. A finite element implementation of the model is validated via MD simulations and then used to investigate the existence of GO representative volume elements (RVE). We find that for the studied GO, an RVE behavior arises for monolayer sizes in excess to 40 nm. Moreover, we reveal that the response of monolayers with two main different functional chemistries, epoxide-rich and hydroxyl-rich, present distinct differences in mechanical behavior. In addition, we explored the role of defect density in GO, and validate the applicability of the model to larger length scales by predicting membrane deflection behavior, in close agreement with previous experimental and theoretical observations. As such the work presents a reduced order modeling framework applicable in the study of mechanical properties and deformation mechanisms in 2D multiphase materials.

The Microstructural Evolution and Mechanical Properties of Zr-Based Metallic Glass under Different Strain Rate Compressions

PubMed Central

Chen, Tao-Hsing; Tsai, Chih-Kai

2015-01-01

In this study, the high strain rate deformation behavior and the microstructure evolution of Zr-Cu-Al-Ni metallic glasses under various strain rates were investigated. The influence of strain and strain rate on the mechanical properties and fracture behavior, as well as microstructural properties was also investigated. Before mechanical testing, the structure and thermal stability of the Zr-Cu-Al-Ni metallic glasses were studied with X-ray diffraction (XRD) and differential scanning calorimeter. The mechanical property experiments and microstructural observations of Zr-Cu-Al-Ni metallic glasses under different strain rates ranging from 10−3 to 5.1 × 103 s−1 and at temperatures of 25 °C were investigated using compressive split-Hopkinson bar (SHPB) and an MTS tester. An in situ transmission electron microscope (TEM) nanoindenter was used to carry out compression tests and investigate the deformation behavior arising at nanopillars of the Zr-based metallic glass. The formation and interaction of shear band during the plastic deformation were investigated. Moreover, it was clearly apparent that the mechanical strength and ductility could be enhanced by impeding the penetration of shear bands with reinforced particles. PMID:28788034

Electrospun microcrimped fibers with nonlinear mechanical properties enhance ligament fibroblast phenotype.

PubMed

Grace Chao, Pen-hsiu; Hsu, Hsiang-Yi; Tseng, Hsiao-Yun

2014-09-01

Fiber structure and order greatly impact the mechanical behavior of fibrous materials. In biological tissues, the nonlinear mechanics of fibrous scaffolds contribute to the functionality of the material. The nonlinear mechanical properties of the wavy structure (crimp) in collagen allow tissue flexibility while preventing over-extension. A number of approaches have tried to recreate this complex mechanical functionality. We generated microcrimped fibers by briefly heating electrospun parallel fibers over the glass transition temperature or by ethanol treatment. The crimp structure is similar to those of collagen fibers found in native aorta, intestines, or ligaments. Using poly-L-lactic acid fibers, we demonstrated that the bulk materials exhibit changed stress-strain behaviors with a significant increase in the toe region in correlation to the degree of crimp, similar to those observed in collagenous tissues. In addition to mimicking the stress-strain behavior of biological tissues, the microcrimped fibers are instructive in cell morphology and promote ligament phenotypic gene expression. This effect can be further enhanced by dynamic tensile loading, a physiological perturbation in vivo. This rapid and economical approach for microcrimped fiber production provides an accessible platform to study structure-function relationships and a novel functional scaffold for tissue engineering and cell mechanobiology studies.

A novel dental implant abutment with micro-motion capability--development and biomechanical evaluations.

PubMed

Chen, Yen-Yin; Chen, Weng-Pin; Chang, Hao-Hueng; Huang, Shih-Hao; Lin, Chun-Pin

2014-02-01

The aim of this study was to develop a novel dental implant abutment with a micro-motion mechanism that imitates the biomechanical behavior of the periodontal ligament, with the goal of increasing the long-term survival rate of dental implants. Computer-aided design software was used to design a novel dental implant abutment with an internal resilient component with a micro-motion capability. The feasibility of the novel system was investigated via finite element analysis. Then, a prototype of the novel dental implant abutment was fabricated, and the mechanical behavior was evaluated. The results of the mechanical tests and finite element analysis confirmed that the novel dental implant abutment possessed the anticipated micro-motion capability. Furthermore, the nonlinear force-displacement behavior apparent in this micro-motion mechanism imitated the movement of a human tooth. The slope of the force-displacement curve of the novel abutment was approximately 38.5 N/mm before the 0.02-mm displacement and approximately 430 N/mm after the 0.03-mm displacement. The novel dental implant abutment with a micro-motion mechanism actually imitated the biomechanical behavior of a natural tooth and provided resilient function, sealing, a non-separation mechanism, and ease-of-use. Copyright © 2013 Academy of Dental Materials. All rights reserved.

Meso-Scale Finite Element Analysis of Mechanical Behavior of 3D Braided Composites Subjected to Biaxial Tension Loadings

NASA Astrophysics Data System (ADS)

Zhang, Chao; Curiel-Sosa, Jose L.; Bui, Tinh Quoc

2018-04-01

In many engineering applications, 3D braided composites are designed for primary loading-bearing structures, and they are frequently subjected to multi-axial loading conditions during service. In this paper, a unit-cell based finite element model is developed for assessment of mechanical behavior of 3D braided composites under different biaxial tension loadings. To predict the damage initiation and evolution of braiding yarns and matrix in the unit-cell, we thus propose an anisotropic damage model based on Murakami damage theory in conjunction with Hashin failure criteria and maximum stress criteria. To attain exact stress ratio, force loading mode of periodic boundary conditions which never been attempted before is first executed to the unit-cell model to apply the biaxial tension loadings. The biaxial mechanical behaviors, such as the stress distribution, tensile modulus and tensile strength are analyzed and discussed. The damage development of 3D braided composites under typical biaxial tension loadings is simulated and the damage mechanisms are revealed in the simulation process. The present study generally provides a new reference to the meso-scale finite element analysis (FEA) of multi-axial mechanical behavior of other textile composites.

Experimental characterization and microstructure linked modeling of mechanical behavior of ultra-thin aluminum foils used in packaging

NASA Astrophysics Data System (ADS)

Tabourot, Laurent; Charleux, Ludovic; Balland, Pascale; Sène, Ndèye Awa; Andreasson, Eskil

2018-05-01

This paper is based on the hypothesis that introducing distribution of mechanical properties is beneficial for modeling all kinds of mechanical behavior, even of ordinary metallic materials. To bring proof of its admissibility, it has to be first shown that modeling based on this assertion is able to efficiently describe standard mechanical behavior of materials. Searching for typical study case, it has been assessed that at a low scale, yield stresses could be strongly distributed in ultrathin aluminum foils used in packaging industry, offering opportunities to identifying their distribution and showing its role on the mechanical properties. Considering initially reduced modeling allow to establish a valuable connection between the hardening curve and the distribution of local yield stresses. This serves for finding initial value of distribution parameters in a more sophisticated identification procedure. With finally limited number of representative classes of local yield stresses, concretely 3 is enough, it is shown that a 3D finite element simulation involving limited numbers of elements returns realistic behavior of an ultrathin aluminum foil exerted to tensile test, in reference to experimental results. This gives way to large possibilities in modeling in order to give back complex experimental evidence.

Studies conducted as a search for physical mechanisms relating solar variability and the troposphere

NASA Technical Reports Server (NTRS)

Wu, S. T. (Editor)

1981-01-01

Chains of causative mechanisms that are hypothesized to relate solar variability to the behavior of the Earth's lower atmosphere were assessed. Solar variations believed most likely to constitute the forcing functions in hypothesized solar terrestrial atmosphere chain, changes in the Earth's atmospheric electrical characteristics due to solar variability, and the observed variations in atmospheric behavior that are influenced by solar variability were also examined.

The Evolution of Different Forms of Sociality: Behavioral Mechanisms and Eco-Evolutionary Feedback

PubMed Central

van der Post, Daniel J.; Verbrugge, Rineke; Hemelrijk, Charlotte K.

2015-01-01

Different forms of sociality have evolved via unique evolutionary trajectories. However, it remains unknown to what extent trajectories of social evolution depend on the specific characteristics of different species. Our approach to studying such trajectories is to use evolutionary case-studies, so that we can investigate how grouping co-evolves with a multitude of individual characteristics. Here we focus on anti-predator vigilance and foraging. We use an individual-based model, where behavioral mechanisms are specified, and costs and benefits are not predefined. We show that evolutionary changes in grouping alter selection pressures on vigilance, and vice versa. This eco-evolutionary feedback generates an evolutionary progression from “leader-follower” societies to “fission-fusion” societies, where cooperative vigilance in groups is maintained via a balance between within- and between-group selection. Group-level selection is generated from an assortment that arises spontaneously when vigilant and non-vigilant foragers have different grouping tendencies. The evolutionary maintenance of small groups, and cooperative vigilance in those groups, is therefore achieved simultaneously. The evolutionary phases, and the transitions between them, depend strongly on behavioral mechanisms. Thus, integrating behavioral mechanisms and eco-evolutionary feedback is critical for understanding what kinds of intermediate stages are involved during the evolution of particular forms of sociality. PMID:25629313

The evolution of different forms of sociality: behavioral mechanisms and eco-evolutionary feedback.

PubMed

van der Post, Daniel J; Verbrugge, Rineke; Hemelrijk, Charlotte K

2015-01-01

Different forms of sociality have evolved via unique evolutionary trajectories. However, it remains unknown to what extent trajectories of social evolution depend on the specific characteristics of different species. Our approach to studying such trajectories is to use evolutionary case-studies, so that we can investigate how grouping co-evolves with a multitude of individual characteristics. Here we focus on anti-predator vigilance and foraging. We use an individual-based model, where behavioral mechanisms are specified, and costs and benefits are not predefined. We show that evolutionary changes in grouping alter selection pressures on vigilance, and vice versa. This eco-evolutionary feedback generates an evolutionary progression from "leader-follower" societies to "fission-fusion" societies, where cooperative vigilance in groups is maintained via a balance between within- and between-group selection. Group-level selection is generated from an assortment that arises spontaneously when vigilant and non-vigilant foragers have different grouping tendencies. The evolutionary maintenance of small groups, and cooperative vigilance in those groups, is therefore achieved simultaneously. The evolutionary phases, and the transitions between them, depend strongly on behavioral mechanisms. Thus, integrating behavioral mechanisms and eco-evolutionary feedback is critical for understanding what kinds of intermediate stages are involved during the evolution of particular forms of sociality.

Mechanisms That Link Parenting Practices to Adolescents' Risky Sexual Behavior: A Test of Six Competing Theories.

PubMed

Simons, Leslie Gordon; Sutton, Tara E; Simons, Ronald L; Gibbons, Frederick X; Murry, Velma McBride

2016-02-01

Risky sexual behavior, particularly among adolescents, continues to be a major source of concern. In order to develop effective education and prevention programs, there is a need for research that identifies the antecedents of such behavior. This study investigated the mediators that link parenting experiences during early adolescence to subsequent risky sexual behaviors among a diverse sample of African American youth (N = 629, 55 % female). While there is ample evidence that parenting practices (e.g., supportive parenting, harsh parenting, parental management) are antecedent to risky sexual behavior, few studies have examined whether one approach to parenting is more strongly related to risky sex than others. Using a developmental approach, the current study focused on factors associated with six theories of risky sexual behavior. While past research has provided support for all of the theories, few studies have assessed the relative contribution of each while controlling for the processes proposed by the others. The current study addresses these gaps in the literature and reports results separately by gender. Longitudinal analyses using structural equation modeling revealed that the mediating mechanisms associated with social learning and attachment theories were significantly related to the risky sexual behavior of males and females. Additionally, there was support for social control and self-control theories only for females and for life history theory only for males. We did not find support for problem behavior theory, a perspective that dominates the risky sex literature, after controlling for the factors associated with the other theories. Finally, supportive parenting emerged as the parenting behavior most influential with regard to adolescents' risky sexual behavior. These results provide insight regarding efficacious approaches to education and preventative programs designed to reduce risky sexual behaviors among adolescents.

Tribocorrosion behavior of beta titanium biomedical alloys in phosphate buffer saline solution.

PubMed

Pina, V Guiñón; Dalmau, A; Devesa, F; Amigó, V; Muñoz, A Igual

2015-06-01

The tribo-electrochemical behavior of different β titanium alloys for biomedical applications sintered by powder metallurgy has been investigated. Different mechanical, electrochemical and optical techniques were used to study the influence of the chemical composition, Sn content, and the electrochemical conditions on the tribocorrosion behavior of those alloys Ti30NbxSn alloys (where "x" is the weight percentage of Sn content, 2% and 4%). Sn content increases the active and passive dissolution rate of the titanium alloys, thus increasing the mechanically activated corrosion under tribocorrosion conditions. It also increases the mechanical wear of the alloy. Prevailing electrochemical conditions between -1 and 2V influences the wear accelerated corrosion by increasing it with the applied potential and slightly increases the mechanical wear of Ti30Nb4Sn. Wear accelerated corrosion can be predicted by existing models as a function of electrochemical and mechanical parameters of the titanium alloys. Copyright © 2015 Elsevier Ltd. All rights reserved.

Optical assessment of tissue mechanics: acousto-optical elastography of skin

NASA Astrophysics Data System (ADS)

Kirkpatrick, Sean J.

2003-10-01

A multiphysics approach, combining acoustics, optics, and mechanics can be used to detect regions of skin with distinct mechanical behavior that may indicate a pathology, such as a cancerous skin lesion. Herein, an acousto - optical approach to evaluating the viscoelastic behavior of superficial skin layers will be presented. The method relies upon inducing low frequency guided surface waves in the skin and detecting these waves by monitoring the shift in the backscattered laser speckle pattern created by illuminating a small region of the skin with coherent light. Artificial lesions in the form of chemical cross-linking and chemical softening were induced in superficial porcine skin layers and detected based upon variations in local mechanical behavior. The lesions affect not only the time-of-flight of the guided surface waves, but also change the relative phase of the acoustic waves as determined optically. The method may be applicable in the study and diagnosis of superficial skin lesions.

Crystalline-like temperature dependence of the electrical characteristics in amorphous Indium-Gallium-Zinc-Oxide thin film transistors

NASA Astrophysics Data System (ADS)

Estrada, M.; Hernandez-Barrios, Y.; Cerdeira, A.; Ávila-Herrera, F.; Tinoco, J.; Moldovan, O.; Lime, F.; Iñiguez, B.

2017-09-01

A crystalline-like temperature dependence of the electrical characteristics of amorphous Indium-Gallium-Zinc-Oxide (a-IGZO) thin film transistors (TFTs) is reported, in which the drain current reduces as the temperature is increased. This behavior appears for values of drain and gate voltages above which a change in the predominant conduction mechanism occurs. After studying the possible conduction mechanisms, it was determined that, for gate and drain voltages below these values, hopping is the predominant mechanism with the current increasing with temperature, while for values above, the predominant conduction mechanism becomes percolation in the conduction band or band conduction and IDS reduces as the temperature increases. It was determined that this behavior appears, when the effect of trapping is reduced, either by varying the density of states, their characteristic energy or both. Simulations were used to further confirm the causes of the observed behavior.

Antiepileptic drug effects on mood and behavior: molecular targets.

PubMed

Perucca, Piero; Mula, Marco

2013-03-01

With almost 100 years of clinical experience, antiepileptic drugs (AEDs) remain the mainstay of epilepsy treatment. They suppress epileptic seizures by acting on a variety of mechanisms and molecular targets involved in the regulation of neuronal excitability. These include inhibitory-GABAergic and excitatory-glutamatergic neurotransmission, as well as ion (sodium and calcium) conductance through voltage-gated channels. On the other hand, accruing evidence indicates that these mechanisms and targets are also implicated in the regulation of mood and behavior, which may explain why each AED is associated with specific psychotropic effects. These effects, however, cannot be explained solely on the basis of the known mode of action of each AED, and other mechanisms or targets are likely to be implicated. In this article, we review positive and negative effects of AEDs on mood and behavior, discuss putative underlying mechanisms, and highlight knowledge gaps which should be addressed in future studies. Copyright © 2012 Elsevier Inc. All rights reserved.

Mechanical behavior simulation of MEMS-based cantilever beam using COMSOL multiphysics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Acheli, A., E-mail: aacheli@cdta.dz; Serhane, R.

This paper presents the studies of mechanical behavior of MEMS cantilever beam made of poly-silicon material, using the coupling of three application modes (plane strain, electrostatics and the moving mesh) of COMSOL Multi-physics software. The cantilevers playing a key role in Micro Electro-Mechanical Systems (MEMS) devices (switches, resonators, etc) working under potential shock. This is why they require actuation under predetermined conditions, such as electrostatic force or inertial force. In this paper, we present mechanical behavior of a cantilever actuated by an electrostatic force. In addition to the simplification of calculations, the weight of the cantilever was not taken intomore » account. Different parameters like beam displacement, electrostatics force and stress over the beam have been calculated by finite element method after having defining the geometry, the material of the cantilever model (fixed at one of ends but is free to move otherwise) and his operational space.« less

Pair distribution function study and mechanical behavior of as-cast and structurally relaxed Zr-based bulk metallic glasses

NASA Astrophysics Data System (ADS)

Fan, Cang; Liaw, P. K.; Wilson, T. W.; Choo, H.; Gao, Y. F.; Liu, C. T.; Proffen, Th.; Richardson, J. W.

2006-12-01

Contrary to reported results on structural relaxation inducing brittleness in amorphous alloys, the authors found that structural relaxation actually caused an increase in the strength of Zr55Cu35Al10 bulk metallic glass (BMG) without changing the plasticity. Three dimensional models were rebuilt for the as-cast and structurally relaxed BMGs by reverse Monte Carlo (RMC) simulations based on the pair distribution function (PDF) measured by neutron scattering. Only a small portion of the atom pairs was found to change to more dense packing. The concept of free volume was defined based on the PDF and RMC studies, and the mechanism of mechanical behavior was discussed.

Tension-compression viscoelastic behaviors of the periodontal ligament.

PubMed

Wang, Chen-Ying; Su, Ming-Zen; Chang, Hao-Hueng; Chiang, Yu-Chih; Tao, Shao-Huan; Cheng, Jung-Ho; Fuh, Lih-Jyh; Lin, Chun-Pin

2012-09-01

Although exhaustively studied, the mechanism responsible for tooth support and the mechanical properties of the periodontal ligament (PDL) remain a subject of considerable controversy. In the past, various experimental techniques and theoretical analyses have been employed to tackle this intricate problem. The aim of this study was to investigate the viscoelastic behaviors of the PDL using three-dimensional finite element analysis. Three dentoalveolar complex models were established to simulate the tissue behaviors of the PDL: (1) deviatoric viscoelastic model; (2) volumetric viscoelastic model; and (3) tension-compression volumetric viscoelastic model. These modified models took into consideration the presence of tension and compression along the PDL during both loading and unloading. The inverse parameter identification process was developed to determine the mechanical properties of the PDL from the results of previously reported in vitro and in vivo experiments. The results suggest that the tension-compression volumetric viscoelastic model is a good approximation of normal PDL behavior during the loading-unloading process, and the deviatoric viscoelastic model is a good representation of how a damaged PDL behaves under loading conditions. Moreover, fluid appears to be the main creep source in the PDL. We believe that the biomechanical properties of the PDL established via retrograde calculation in this study can lead to the construction of more accurate extra-oral models and a comprehensive understanding of the biomechanical behavior of the PDL. Copyright © 2012. Published by Elsevier B.V.

Nonlinear mechanics of a ring structure subjected to multi-pairs of evenly distributed equal radial forces

NASA Astrophysics Data System (ADS)

Chen, Q.; Sun, F.; Li, Z. Y.; Taxis, L.; Pugno, N.

2017-10-01

Combining the elastica theory, finite element (FE) analysis, and a geometrical topological experiment, we studied the mechanical behavior of a ring subjected to multi-pairs of evenly distributed equal radial forces by looking at its seven distinct states. The results showed that the theoretical predictions of the ring deformation and strain energy matched the FE results very well, and that the ring deformations were comparable to the topological experiment. Moreover, no matter whether the ring was compressed or tensioned by N-pairs of forces, the ring always tended to be regular polygons with 2 N sides as the force increased, and a proper compressive force deformed the ring into exquisite flower-like patterns. The present study solves a basic mechanical problem of a ring subjected to lateral forces, which can be useful for studying the relevant mechanical behavior of ring structures from the nano- to the macro-scale.

Order Information in Working Memory: An Integrative Review of Evidence From Brain and Behavior

ERIC Educational Resources Information Center

Marshuetz, Christy

2005-01-01

Evidence about memory for order information comes from a number of different methodologies: human cognition, patient studies, neuroimaging studies, and animal lesion and behavioral studies. The present article discusses (a) evidence that order and item memory are separable; (b) proposed mechanisms for order memory (interitem associations, direct…

Peeling mechanism of tomato under infrared heating

USDA-ARS?s Scientific Manuscript database

Critical behaviors of peeling tomatoes using infrared heat are thermally induced peel loosening and subsequent cracking. However, the mechanism of peel loosening and cracking due to infrared heating remains unclear. This study aimed at investigating the mechanism of peeling tomatoes under infrared h...

Mechanical characterization and modeling for anodes and cathodes in lithium-ion batteries

NASA Astrophysics Data System (ADS)

Wang, Lubing; Yin, Sha; Zhang, Chao; Huan, Yong; Xu, Jun

2018-07-01

Mechanical properties of electrode materials have significant influence over electrochemical properties as well as mechanical integrity of lithium-ion battery cells. Here, anode and cathode in a commercially available 18650 NCA (Nickel Cobalt Aluminum Oxide)/graphite cell were comprehensively studied by tensile tests considering material anisotropy, SOC (state of charge), strain rate and electrolyte content. Results showed that the mechanical properties of both electrodes were highly dependent on strain rate and electrolyte content; however, anode was SOC dependent while cathode was not. Besides, coupled effects of strain rate and SOC of anodes were also discussed. SEM (scanning electron microscope) images of surfaces and cross-sections of electrodes showed the fracture morphology. In addition, mechanical behavior of Cu foil separated from anode with different SOC values were studied and compared. Finally, constitutive models of electrodes considering both strain rate and anisotropy effects were established. This study reveals the relationship between electrochemical dependent mechanical behavior of the electrodes. The established mechanical models of electrodes can be applied to the numerical computation of battery cells. Results are essential to predict the mechanical responses as well as the deformation of battery cell under various loading conditions, facilitating safer battery design and manufacturing.

The work is never ending: uncovering teamwork sustainability using realistic evaluation.

PubMed

Frykman, Mandus; von Thiele Schwarz, Ulrica; Muntlin Athlin, Åsa; Hasson, Henna; Mazzocato, Pamela

2017-03-20

Purpose The purpose of this paper is to uncover the mechanisms influencing the sustainability of behavior changes following the implementation of teamwork. Design/methodology/approach Realistic evaluation was combined with a framework (DCOM®) based on applied behavior analysis to study the sustainability of behavior changes two and a half years after the initial implementation of teamwork at an emergency department. The DCOM® framework was used to categorize the mechanisms of behavior change interventions (BCIs) into the four categories of direction, competence, opportunity, and motivation. Non-participant observation and interview data were used. Findings The teamwork behaviors were not sustained. A substantial fallback in managerial activities in combination with a complex context contributed to reduced direction, opportunity, and motivation. Reduced direction made staff members unclear about how and why they should work in teams. Deterioration of opportunity was evident from the lack of problem-solving resources resulting in accumulated barriers to teamwork. Motivation in terms of management support and feedback was reduced. Practical implications The implementation of complex organizational changes in complex healthcare contexts requires continuous adaption and managerial activities well beyond the initial implementation period. Originality/value By integrating the DCOM® framework with realistic evaluation, this study responds to the call for theoretically based research on behavioral mechanisms that can explain how BCIs interact with context and how this interaction influences sustainability.

Neural Substrates of Sexual Desire in Individuals with Problematic Hypersexual Behavior

PubMed Central

Seok, Ji-Woo; Sohn, Jin-Hun

2015-01-01

Studies on the characteristics of individuals with hypersexual disorder have been accumulating due to increasing concerns about problematic hypersexual behavior (PHB). Currently, relatively little is known about the underlying behavioral and neural mechanisms of sexual desire. Our study aimed to investigate the neural correlates of sexual desire with event-related functional magnetic resonance imaging (fMRI). Twenty-three individuals with PHB and 22 age-matched healthy controls were scanned while they passively viewed sexual and nonsexual stimuli. The subjects' levels of sexual desire were assessed in response to each sexual stimulus. Relative to controls, individuals with PHB experienced more frequent and enhanced sexual desire during exposure to sexual stimuli. Greater activation was observed in the caudate nucleus, inferior parietal lobe, dorsal anterior cingulate gyrus, thalamus, and dorsolateral prefrontal cortex in the PHB group than in the control group. In addition, the hemodynamic patterns in the activated areas differed between the groups. Consistent with the findings of brain imaging studies of substance and behavior addiction, individuals with the behavioral characteristics of PHB and enhanced desire exhibited altered activation in the prefrontal cortex and subcortical regions. In conclusion, our results will help to characterize the behaviors and associated neural mechanisms of individuals with PHB. PMID:26648855

Translation and cultural adaptation of the Brazilian Portuguese version of the Behavioral Pain Scale.

PubMed

Morete, Márcia Carla; Mofatto, Sarah Camargo; Pereira, Camila Alves; Silva, Ana Paula; Odierna, Maria Tereza

2014-01-01

The objective of this study was to translate and culturally adapt the Behavioral Pain Scale to Brazilian Portuguese and to evaluate the psychometric properties of this scale. This study was conducted in two phases: the Behavioral Pain Scale was translated and culturally adapted to Brazilian Portuguese and the psychometric properties of this scale were subsequently assessed (reliability and clinical utility). The study sample consisted of 100 patients who were older than 18 years of age, admitted to an intensive care unit, intubated, mechanically ventilated, and subjected or not to sedation and analgesia from July 2012 to December 2012. Pediatric and non-intubated patients were excluded. The study was conducted at a large private hospital that was situated in the city of São Paulo (SP). Regarding reproducibility, the results revealed that the observed agreement between the two evaluators was 92.08% for the pain descriptor "adaptation to mechanical ventilation", 88.1% for "upper limbs", and 90.1% for "facial expression". The kappa coefficient of agreement for "adaptation to mechanical ventilation" assumed a value of 0.740. Good agreement was observed between the evaluators with an intraclass correlation coefficient of 0.807 (95% confidence interval: 0.727-0.866). The Behavioral Pain Scale was easy to administer and reproduce. Additionally, this scale had adequate internal consistency. The Behavioral Pain Scale was satisfactorily adapted to Brazilian Portuguese for the assessment of pain in critically ill patients.

Marital Conflict in Early Childhood and Adolescent Disordered Eating: Emotional Insecurity about the Marital Relationship as an Explanatory Mechanism

PubMed Central

George, Melissa W.; Fairchild, Amanda J.; Cummings, E. Mark; Davies, Patrick T.

2017-01-01

Disordered eating behaviors, including frequent dieting, unhealthy weight control behaviors (e.g., vomiting and skipping meals for weight loss) and binge eating are prevalent among adolescents. While negative, conflict-ridden family environments have long been implicated as problematic and a contributing factor to the development of disordered eating, few studies have examined the influence of marital conflict exposure in childhood to understand the development of these behaviors in adolescence. The current study investigates the impact of marital conflict, children’s emotional insecurity about the marital relationship, and disordered eating behaviors in early adolescence in a prospective, longitudinal study of a community sample of 236 families in Midwest and Northeast regions of the U.S. Full structural mediation analyses utilizing robust latent constructs of marital conflict and emotional insecurity about the marital relationship, support children’s emotional insecurity as an explanatory mechanism for the influence of marital conflict on adolescent disordered eating behaviors. Findings are discussed with important implications for the long-term impact of marital conflict and the development of disordered eating in adolescence. PMID:25113902

Marital conflict in early childhood and adolescent disordered eating: emotional insecurity about the marital relationship as an explanatory mechanism.

PubMed

George, Melissa W; Fairchild, Amanda J; Mark Cummings, E; Davies, Patrick T

2014-12-01

Disordered eating behaviors, including frequent dieting, unhealthy weight control behaviors (e.g., vomiting and skipping meals for weight loss) and binge eating are prevalent among adolescents. While negative, conflict-ridden family environments have long been implicated as problematic and a contributing factor to the development of disordered eating, few studies have examined the influence of marital conflict exposure in childhood to understand the development of these behaviors in adolescence. The current study investigates the impact of marital conflict, children's emotional insecurity about the marital relationship, and disordered eating behaviors in early adolescence in a prospective, longitudinal study of a community sample of 236 families in Midwest and Northeast regions of the U.S. Full structural mediation analyses utilizing robust latent constructs of marital conflict and emotional insecurity about the marital relationship, support children's emotional insecurity as an explanatory mechanism for the influence of marital conflict on adolescent disordered eating behaviors. Findings are discussed with important implications for the long-term impact of marital conflict and the development of disordered eating in adolescence. Copyright © 2014 Elsevier Ltd. All rights reserved.

From behavior to neural dynamics: An integrated theory of attention

PubMed Central

Buschman, Timothy J.; Kastner, Sabine

2015-01-01

The brain has a limited capacity and therefore needs mechanisms to selectively enhance the information most relevant to one’s current behavior. We refer to these mechanisms as ‘attention’. Attention acts by increasing the strength of selected neural representations and preferentially routing them through the brain’s large-scale network. This is a critical component of cognition and therefore has been a central topic in cognitive neuroscience. Here we review a diverse literature that has studied attention at the level of behavior, networks, circuits and neurons. We then integrate these disparate results into a unified theory of attention. PMID:26447577

Structural and synaptic plasticity in stress-related disorders

PubMed Central

Christoffel, Daniel J.; Golden, Sam A.; Russo, Scott J.

2011-01-01

Stress can have a lasting impact on the structure and function of brain circuitry that results in long-lasting changes in the behavior of an organism. Synaptic plasticity is the mechanism by which information is stored and maintained within individual synapses, neurons, and neuronal circuits to guide the behavior of an organism. Although these mechanisms allow the organism to adapt to its constantly evolving environment, not all of these adaptations are beneficial. Under prolonged bouts of physical or psychological stress, these mechanisms become dysregulated, and the connectivity between brain regions becomes unbalanced, resulting in pathological behaviors. In this review, we highlight the effects of stress on the structure and function of neurons within the mesocorticolimbic brain systems known to regulate mood and motivation. We then discuss the implications of these spine adaptations on neuronal activity and pathological behaviors implicated in mood disorders. Finally, we end by discussing recent brain imaging studies in human depression within the context of these basic findings to provide insight into the underlying mechanisms leading to neural dysfunction in depression. PMID:21967517

Genetics of Aggression in Voles

PubMed Central

Gobrogge, Kyle L.; Wang, Zuoxin

2016-01-01

Prairie voles (Microtus ochrogaster) are socially monogamous rodents that form pair bonds—a behavior composed of several social interactions including attachment with a familiar mate and aggression toward conspecific strangers. Therefore, this species has provided an excellent opportunity for the study of pair bonding behavior and its underlying neural mechanisms. In this chapter, we discuss the utility of this unique animal model in the study of aggression and review recent findings illustrating the neurochemical mechanisms underlying pair bonding-induced aggression. Implications of this research for our understanding of the neurobiology of human violence are also discussed. PMID:22078479

The role of religiosity in the relationship between parents, peers, and adolescent risky sexual behavior.

PubMed

Landor, Antoinette; Simons, Leslie Gordon; Simons, Ronald L; Brody, Gene H; Gibbons, Frederick X

2011-03-01

Research has documented a negative relationship between religion and risky sexual behavior. Few studies, however, have examined the processes whereby religion exerts this effect. The present study develops and tests a model of various mechanisms whereby parental religiosity reduces the likelihood of adolescents' participation in risky sexual behavior (early sexual debut, multiple sexual partners, and inconsistent condom use). Structural equation modeling, using longitudinal data from a sample of 612 African American adolescents (55% female), provided support for the model. The results indicated that parental religiosity influenced adolescent risky sexual behavior through its impact on authoritative parenting, adolescent religiosity, and adolescent affiliation with less sexually permissive peers. Some mediating mechanisms differed by the gender of the respondent, suggesting a "double-standard" for daughters but not for sons. Findings also indicated the importance of messages about sexual behavior that are transmitted to adolescents by their peers. Theoretical and policy implications of the findings are discussed.

The Role of Religiosity in the Relationship Between Parents, Peers, and Adolescent Risky Sexual Behavior

PubMed Central

Simons, Leslie Gordon; Simons, Ronald L.; Brody, Gene H.; Gibbons, Frederick X.

2012-01-01

Research has documented a negative relationship between religion and risky sexual behavior. Few studies, however, have examined the processes whereby religion exerts this effect. The present study develops and tests a model of various mechanisms whereby parental religiosity reduces the likelihood of adolescents’ participation in risky sexual behavior (early sexual debut, multiple sexual partners, and inconsistent condom use). Structural equation modeling, using longitudinal data from a sample of 612 African American adolescents (55% female), provided support for the model. The results indicated that parental religiosity influenced adolescent risky sexual behavior through its impact on authoritative parenting, adolescent religiosity, and adolescent affiliation with less sexually permissive peers. Some mediating mechanisms differed by the gender of the respondent, suggesting a “double-standard” for daughters but not for sons. Findings also indicated the importance of messages about sexual behavior that are transmitted to adolescents by their peers. Theoretical and policy implications of the findings are discussed. PMID:21052800

Low cycle fatigue behavior of a ferritic reactor pressure vessel steel

NASA Astrophysics Data System (ADS)

Sarkar, Apu; Kumawat, Bhupendra K.; Chakravartty, J. K.

2015-07-01

The cyclic stress-strain response and the low cycle fatigue (LCF) behavior of 20MnMoNi55 pressure vessel steel were studied. Tensile strength and LCF properties were examined at room temperature (RT) using specimens cut from rolling direction of a rolled block. The fully reversed strain-controlled LCF tests were conducted at a constant total strain rate with different axial strain amplitude levels. The cyclic strain-stress relationships and the strain-life relationships were obtained through the test results, and related LCF parameters of the steel were calculated. The studied steel exhibits cyclic softening behavior. Furthermore, analysis of stabilized hysteresis loops showed that the steel exhibits non-Masing behavior. Complementary scanning electron microscopy examinations were also carried out on fracture surfaces to reveal dominant damage mechanisms during crack initiation, propagation and fracture. Multiple crack initiation sites were observed on the fracture surface. The investigated LCF behavior can provide reference for pressure vessel life assessment and fracture mechanisms analysis.

Genetic influences on adolescent sexual behavior: Why genes matter for environmentally oriented researchers.

PubMed

Harden, K Paige

2014-03-01

There are dramatic individual differences among adolescents in how and when they become sexually active adults, and early sexual activity is frequently cited as a cause of concern for scientists, policymakers, and the general public. Understanding the causes and developmental impact of adolescent sexual activity can be furthered by considering genes as a source of individual differences. Quantitative behavioral genetics (i.e., twin and family studies) and candidate gene association studies now provide clear evidence for the genetic underpinnings of individual differences in adolescent sexual behavior and related phenotypes. Genetic influences on sexual behavior may operate through a variety of direct and indirect mechanisms, including pubertal development, testosterone levels, and dopaminergic systems. Genetic differences may be systematically associated with exposure to environments that are commonly treated as causes of sexual behavior (gene-environment correlation). Possible gene-environment correlations pose a serious challenge for interpreting the results of much behavioral research. Multivariate, genetically informed research on adolescent sexual behavior compares twins and family members as a form of quasi experiment: How do twins who differ in their sexual experiences differ in their later development? The small but growing body of genetically informed research has already challenged dominant assumptions regarding the etiology and sequelae of adolescent sexual behavior, with some studies indicating possible positive effects of teenage sexuality. Studies of Gene × Environment interaction may further elucidate the mechanisms by which genes and environments combine to shape the development of sexual behavior and its psychosocial consequences. Overall, the existence of heritable variation in adolescent sexual behavior has profound implications for environmentally oriented theory and research.

Latent class analysis of eating and impulsive behavioral symptoms in Taiwanese women with bulimia nervosa.

PubMed

Tseng, Mei-Chih Meg; Hu, Fu-Chang

2012-01-01

The implications of impulsivity in its relationship with binge-eating or purging behaviors remain unclear. This study examined the patterns of eating behaviors and co-morbid impulsive behaviors in individuals with bulimia nervosa n optimally homogeneous classes using latent class analysis (LCA). All participants (n=180) were asked to complete a series of self-reported inventories of impulsive behaviors and other psychological measures. Information regarding the lifetime presence of symptoms of eating disorder was assessed by clinical interviews. LCA was conducted using eating disorder symptoms, impulsive behaviors, and the number of purging methods. Three latent classes of bulimic women were identified. These were women who exhibited relatively higher rates of purging, symptoms of impulsive behavior, and multiple purging methods (17.8%), women who used no more than one purging method with a low occurrence of impulsive behavior (41.7%), and women who showed higher rates of purging behaviors and the use of multiple purging methods with a low rate of impulsive behavior (41.7%). The impulsive sub-group had comparable severity of eating-related measures, frequency of binge-eating, and higher levels of general psychopathology than that of the other two sub-groups. This study provides empirical support for the existence of an impulsive subgroup with distinctive features among a non-Western group of BN patients. This study also suggests that mechanisms other than impulse dysregulation may exist for the development of binge-eating and purging behaviors in bulimia nervosa patients, or the mechanisms contributing to binge-eating and impulsive behaviors may be different. Copyright © 2011 Elsevier Inc. All rights reserved.

Integrative Analysis of Genetic, Genomic, and Phenotypic Data for Ethanol Behaviors: A Network-Based Pipeline for Identifying Mechanisms and Potential Drug Targets.

PubMed

Bogenpohl, James W; Mignogna, Kristin M; Smith, Maren L; Miles, Michael F

2017-01-01

Complex behavioral traits, such as alcohol abuse, are caused by an interplay of genetic and environmental factors, producing deleterious functional adaptations in the central nervous system. The long-term behavioral consequences of such changes are of substantial cost to both the individual and society. Substantial progress has been made in the last two decades in understanding elements of brain mechanisms underlying responses to ethanol in animal models and risk factors for alcohol use disorder (AUD) in humans. However, treatments for AUD remain largely ineffective and few medications for this disease state have been licensed. Genome-wide genetic polymorphism analysis (GWAS) in humans, behavioral genetic studies in animal models and brain gene expression studies produced by microarrays or RNA-seq have the potential to produce nonbiased and novel insight into the underlying neurobiology of AUD. However, the complexity of such information, both statistical and informational, has slowed progress toward identifying new targets for intervention in AUD. This chapter describes one approach for integrating behavioral, genetic, and genomic information across animal model and human studies. The goal of this approach is to identify networks of genes functioning in the brain that are most relevant to the underlying mechanisms of a complex disease such as AUD. We illustrate an example of how genomic studies in animal models can be used to produce robust gene networks that have functional implications, and to integrate such animal model genomic data with human genetic studies such as GWAS for AUD. We describe several useful analysis tools for such studies: ComBAT, WGCNA, and EW_dmGWAS. The end result of this analysis is a ranking of gene networks and identification of their cognate hub genes, which might provide eventual targets for future therapeutic development. Furthermore, this combined approach may also improve our understanding of basic mechanisms underlying gene x environmental interactions affecting brain functioning in health and disease.

INTEGRATIVE ANALYSIS OF GENETIC, GENOMIC AND PHENOTYPIC DATA FOR ETHANOL BEHAVIORS: A NETWORK-BASED PIPELINE FOR IDENTIFYING MECHANISMS AND POTENTIAL DRUG TARGETS

PubMed Central

Bogenpohl, James W.; Mignogna, Kristin M.; Smith, Maren L.; Miles, Michael F.

2016-01-01

Complex behavioral traits, such as alcohol abuse, are caused by an interplay of genetic and environmental factors, producing deleterious functional adaptations in the central nervous system. The long-term behavioral consequences of such changes are of substantial cost to both the individual and society. Substantial progress has been made in the last two decades in understanding elements of brain mechanisms underlying responses to ethanol in animal models and risk factors for alcohol use disorder (AUD) in humans. However, treatments for AUD remain largely ineffective and few medications for this disease state have been licensed. Genome-wide genetic polymorphism analysis (GWAS) in humans, behavioral genetic studies in animal models and brain gene expression studies produced by microarrays or RNA-seq have the potential to produce non-biased and novel insight into the underlying neurobiology of AUD. However, the complexity of such information, both statistical and informational, has slowed progress toward identifying new targets for intervention in AUD. This chapter describes one approach for integrating behavioral, genetic, and genomic information across animal model and human studies. The goal of this approach is to identify networks of genes functioning in the brain that are most relevant to the underlying mechanisms of a complex disease such as AUD. We illustrate an example of how genomic studies in animal models can be used to produce robust gene networks that have functional implications, and to integrate such animal model genomic data with human genetic studies such as GWAS for AUD. We describe several useful analysis tools for such studies: ComBAT, WGCNA and EW_dmGWAS. The end result of this analysis is a ranking of gene networks and identification of their cognate hub genes, which might provide eventual targets for future therapeutic development. Furthermore, this combined approach may also improve our understanding of basic mechanisms underlying gene x environmental interactions affecting brain functioning in health and disease. PMID:27933543

Behavior and emotional disturbance in Prader-Willi syndrome.

PubMed

Einfeld, S L; Smith, A; Durvasula, S; Florio, T; Tonge, B J

1999-01-15

To determine if persons with the Prader-Willi syndrome (PWS) have increased psychopathology when compared with matched controls, and whether there is a specific behavior phenotype in PWS, the behavior of 46 persons with PWS was compared with that of control individuals derived from a community sample (N = 454) of persons with mental retardation (MR). Behaviors were studied using the Developmental Behaviour Checklist, an instrument of established validity in the evaluation of behavioral disturbance in individuals with MR. PWS subjects were found to be more behaviorally disturbed than controls overall, and especially in antisocial behavior. In addition, some individual behaviors were more common in PWS subjects than controls. When these behaviors are considered together with findings from other studies using acceptably rigorous methods, a consensus behavior phenotype for PWS can be formulated. This will provide a valid foundation for studies of the mechanism of genetic pathogenesis of behavior in PWS.

Association between Hypothesized Parental Influences and Preschool Children's Physical Activity Behavior

ERIC Educational Resources Information Center

Loprinzi, Paul D.; Schary, David P.; Beets, Michael W.; Leary, Janie; Cardinal, Bradley J.

2013-01-01

Background: To date, most research investigating the influence of parents on children"s physical activity behavior has been conducted among school-aged children. As a result, we have a limited understanding of the mechanisms through which parents can influence their young children's physical activity behavior. The purpose of this study was to…

Community Structural Instability, Anomie, Imitation and Adolescent Suicidal Behavior

ERIC Educational Resources Information Center

Thorlindsson, Thorolfur; Bernburg, Jon Gunnar

2009-01-01

The current study examines the contextual effects of community structural characteristics, as well as the mediating role of key social mechanisms, on youth suicidal behavior in Iceland. We argue that the contextual influence of community structural instability on youth suicidal behavior should be mediated by weak attachment to social norms and…

Identifying Students' Characteristic Learning Behaviors in an Intelligent Tutoring System Fostering Self-Regulated Learning

ERIC Educational Resources Information Center

Bouchet, Francois; Azevedo, Roger; Kinnebrew, John S.; Biswas, Gautam

2012-01-01

Identification of student learning behaviors, especially those that characterize or distinguish students, can yield important insights for the design of adaptation and feedback mechanisms in Intelligent Tutoring Systems (ITS). In this paper, we analyze trace data to identify distinguishing patterns of behavior in a study of 51 college students…

Childhood trauma and problem behavior: Examining the mediating roles of experiential avoidance and mindfulness processes.

PubMed

Roche, Anne I; Kroska, Emily B; Miller, Michelle L; Kroska, Sydney K; O'Hara, Michael W

2018-03-22

Childhood trauma is associated with a variety of risky, unhealthy, or problem behaviors. The current study aimed to explore experiential avoidance and mindfulness processes as mechanisms through which childhood trauma and problem behavior are linked in a college sample. The sample consisted of college-aged young adults recruited November-December, 2016 (N = 414). Participants completed self-report measures of childhood trauma, current problem behavior, experiential avoidance, and mindfulness processes. Bootstrapped mediation analyses examined the mechanistic associations of interest. Mediation analyses indicated that experiential avoidance was a significant mediator of the association between childhood trauma and problem behavior. Additionally, multiple mediation analyses indicated that specific mindfulness facets-act with awareness and nonjudgment of inner experience-significantly mediated the same association. Interventions for college students who have experienced childhood trauma might profitably target mechanisms such as avoidance and mindfulness in order to minimize engagement in problem behavior.

Relaxation mechanisms in glassy dynamics: the Arrhenius and fragile regimes.

PubMed

Hentschel, H George E; Karmakar, Smarajit; Procaccia, Itamar; Zylberg, Jacques

2012-06-01

Generic glass formers exhibit at least two characteristic changes in their relaxation behavior, first to an Arrhenius-type relaxation at some characteristic temperature and then at a lower characteristic temperature to a super-Arrhenius (fragile) behavior. We address these transitions by studying the statistics of free energy barriers for different systems at different temperatures and space dimensions. We present a clear evidence for changes in the dynamical behavior at the transition to Arrhenius and then to a super-Arrhenius behavior. A simple model is presented, based on the idea of competition between single-particle and cooperative dynamics. We argue that Arrhenius behavior can take place as long as there is enough free volume for the completion of a simple T1 relaxation process. Once free volume is absent one needs a cooperative mechanism to "collect" enough free volume. We show that this model captures all the qualitative behavior observed in simulations throughout the considered temperature range.

Neural Mechanism for Stochastic Behavior During a Competitive Game

PubMed Central

Soltani, Alireza; Lee, Daeyeol; Wang, Xiao-Jing

2006-01-01

Previous studies have shown that non-human primates can generate highly stochastic choice behavior, especially when this is required during a competitive interaction with another agent. To understand the neural mechanism of such dynamic choice behavior, we propose a biologically plausible model of decision making endowed with synaptic plasticity that follows a reward-dependent stochastic Hebbian learning rule. This model constitutes a biophysical implementation of reinforcement learning, and it reproduces salient features of behavioral data from an experiment with monkeys playing a matching pennies game. Due to interaction with an opponent and learning dynamics, the model generates quasi-random behavior robustly in spite of intrinsic biases. Furthermore, non-random choice behavior can also emerge when the model plays against a non-interactive opponent, as observed in the monkey experiment. Finally, when combined with a meta-learning algorithm, our model accounts for the slow drift in the animal’s strategy based on a process of reward maximization. PMID:17015181

Polarity effect of electromigration on mechanical properties of lead-free solder joints

NASA Astrophysics Data System (ADS)

Ren, Fei

The trend of electronic packaging is to package the chips and the associated interconnections in a compact way that allows high speed operation; that allows for sufficient heat removal; that can withstand the thermal cycling associated with the turning on and turning off of the circuits; and that protects the circuits from environmental attack. These goals require that flip chip solder joints have higher resistance to electromigration, stronger mechanical property to sustain thermal mechanical stress, and are lead-free materials to satisfy environment and health concern. With lots of work on chemical reaction, electromigration and mechanical study in flip chip solder joints, however, the interaction between different driving forces is still little known. As a matter of fact, the combination study of chemical, electrical and mechanical is more and more significant to the understanding of the behavior of flip chip solder joints. In this dissertation, I developed one dimensional Cu (wire)-eutectic SnAgCu(ball)-Cu(wire) structure to investigate the interaction between electrical and mechanical force in lead-free solder joints. Electromigration was first conducted. The mechanical behaviors of solder joints before, after, and during electromigration were examined. Electrical current and mechanical stress were applied either in serial or in parallel to the solder joints. Tensile, creep, and drop tests, combined with different electrical current densities (1˜5x10 3A/cm2) and different stressing time (3˜144 hours), have been performed to study the effect of electromigration on the mechanical behavior of solder joints. Nano-indentation test was conducted to study the localized mechanical property of IMC at both interfaces in nanometer scale. Fracture images help analyze the failure mechanism of solder joints driven by both electrical and mechanical forces. The combination study shows a strain build-up during electromigration. Furthermore, a ductile-to-brittle transition in flip chip solder joints induced by electromigration is observed, in which the fracture position migrates from the middle to the cathode interface of the joint with increasing current density and time. The transition is explained by the polarity effect of electromigration, particular due to the accumulation of vacancies at the cathode interface.

Statistical model for the mechanical behavior of the tissue engineering non-woven fibrous matrices under large deformation.

PubMed

Rizvi, Mohd Suhail; Pal, Anupam

2014-09-01

The fibrous matrices are widely used as scaffolds for the regeneration of load-bearing tissues due to their structural and mechanical similarities with the fibrous components of the extracellular matrix. These scaffolds not only provide the appropriate microenvironment for the residing cells but also act as medium for the transmission of the mechanical stimuli, essential for the tissue regeneration, from macroscopic scale of the scaffolds to the microscopic scale of cells. The requirement of the mechanical loading for the tissue regeneration requires the fibrous scaffolds to be able to sustain the complex three-dimensional mechanical loading conditions. In order to gain insight into the mechanical behavior of the fibrous matrices under large amount of elongation as well as shear, a statistical model has been formulated to study the macroscopic mechanical behavior of the electrospun fibrous matrix and the transmission of the mechanical stimuli from scaffolds to the cells via the constituting fibers. The study establishes the load-deformation relationships for the fibrous matrices for different structural parameters. It also quantifies the changes in the fiber arrangement and tension generated in the fibers with the deformation of the matrix. The model reveals that the tension generated in the fibers on matrix deformation is not homogeneous and hence the cells located in different regions of the fibrous scaffold might experience different mechanical stimuli. The mechanical response of fibrous matrices was also found to be dependent on the aspect ratio of the matrix. Therefore, the model establishes a structure-mechanics interdependence of the fibrous matrices under large deformation, which can be utilized in identifying the appropriate structure and external mechanical loading conditions for the regeneration of load-bearing tissues. Copyright © 2014 Elsevier Ltd. All rights reserved.

Linear-Nonlinear-Poisson Models of Primate Choice Dynamics

ERIC Educational Resources Information Center

Corrado, Greg S.; Sugrue, Leo P.; Seung, H. Sebastian; Newsome, William T.

2005-01-01

The equilibrium phenomenon of matching behavior traditionally has been studied in stationary environments. Here we attempt to uncover the local mechanism of choice that gives rise to matching by studying behavior in a highly dynamic foraging environment. In our experiments, 2 rhesus monkeys ("Macacca mulatta") foraged for juice rewards by making…

Mechanical properties, morphology, and hydrolytic degradation behavior of polylactic acid / natural rubber blends

NASA Astrophysics Data System (ADS)

Buys, Y. F.; Aznan, A. N. A.; Anuar, H.

2018-01-01

Due to its biodegradability and renewability, polylactic acid (PLA) has been receiving enormous attention as a potential candidate to replace petroleum based polymers. However, PLA has limitation due to its inherent brittleness. In order to overcome this limitation, blending PLA with elastomeric materials such as natural rubber (NR) are commonly reported. In previous, several researches on PLA/NR blend had been reported, with most of them evaluated the mechanical properties. On the other hand, study of degradation behavior is significance of importance, as controlling materials degradation is required in some applications. This research studied the effect of blend composition on mechanical properties, morphology development, and hydrolytic degradation behavior of PLA/NR blends. Various compositions of PLA/NR blends were prepared by melt blending technique. Tensile test and impact test of the blends were performed to evaluate the mechanical properties. Addition of NR improved the elongation at break and impact strength of the blends, but reduced the tensile strength and stiffness of the specimens. Dynamic Mechanical Analysis (DMA) measurements of the blends displayed two peaks at temperature -70˚C which corresponded to T g of NR and 65˚C which corresponded to T g of PLA. Field Emission Scanning Electron Microscopy (FE-SEM) micrograph of 70/30 PLA/NR specimen also showed two distinct phases, which lead to indication that PLA/NR blends are immiscible. Hydrolytic degradation behavior was evaluated by measuring the remaining weight of the samples immersed in sodium hydroxide solution for a predetermined times. It was shown that the degradation behavior of PLA/NR blends is affected by composition of the blends, with 100 PLA and 70/30 PLA/NR blend showed the fastest degradation rate and 100 NR displayed the slowest one.

Feedback and efficient behavior

PubMed Central

2017-01-01

Feedback is an effective tool for promoting efficient behavior: it enhances individuals’ awareness of choice consequences in complex settings. Our study aims to isolate the mechanisms underlying the effects of feedback on achieving efficient behavior in a controlled environment. We design a laboratory experiment in which individuals are not aware of the consequences of different alternatives and, thus, cannot easily identify the efficient ones. We introduce feedback as a mechanism to enhance the awareness of consequences and to stimulate exploration and search for efficient alternatives. We assess the efficacy of three different types of intervention: provision of social information, manipulation of the frequency, and framing of feedback. We find that feedback is most effective when it is framed in terms of losses, that it reduces efficiency when it includes information about inefficient peers’ behavior, and that a lower frequency of feedback does not disrupt efficiency. By quantifying the effect of different types of feedback, our study suggests useful insights for policymakers. PMID:28430787

The contributions of cognitive neuroscience and neuroimaging to understanding mechanisms of behavior change in addiction.

PubMed

Morgenstern, Jon; Naqvi, Nasir H; Debellis, Robert; Breiter, Hans C

2013-06-01

In the last decade, there has been an upsurge of interest in understanding the mechanisms of behavior change (MOBC) and effective behavioral interventions as a strategy to improve addiction-treatment efficacy. However, there remains considerable uncertainty about how treatment research should proceed to address the MOBC issue. In this article, we argue that limitations in the underlying models of addiction that inform behavioral treatment pose an obstacle to elucidating MOBC. We consider how advances in the cognitive neuroscience of addiction offer an alternative conceptual and methodological approach to studying the psychological processes that characterize addiction, and how such advances could inform treatment process research. In addition, we review neuroimaging studies that have tested aspects of neurocognitive theories as a strategy to inform addiction therapies and discuss future directions for transdisciplinary collaborations across cognitive neuroscience and MOBC research. 2013 APA, all rights reserved

The Contributions of Cognitive Neuroscience and Neuroimaging to Understanding Mechanisms of Behavior Change in Addiction

PubMed Central

Morgenstern, Jon; Naqvi, Nasir H.; Debellis, Robert; Breiter, Hans C.

2013-01-01

In the last decade, there has been an upsurge of interest in understanding the mechanisms of behavior change (MOBC) and effective behavioral interventions as a strategy to improve addiction-treatment efficacy. However, there remains considerable uncertainty about how treatment research should proceed to address the MOBC issue. In this article, we argue that limitations in the underlying models of addiction that inform behavioral treatment pose an obstacle to elucidating MOBC. We consider how advances in the cognitive neuroscience of addiction offer an alternative conceptual and methodological approach to studying the psychological processes that characterize addiction, and how such advances could inform treatment process research. In addition, we review neuroimaging studies that have tested aspects of neurocognitive theories as a strategy to inform addiction therapies and discuss future directions for transdisciplinary collaborations across cognitive neuroscience and MOBC research. PMID:23586452

Sleep Fragmentation Exacerbates Mechanical Hypersensitivity and Alters Subsequent Sleep-Wake Behavior in a Mouse Model of Musculoskeletal Sensitization

PubMed Central

Sutton, Blair C.; Opp, Mark R.

2014-01-01

Study Objectives: Sleep deprivation, or sleep disruption, enhances pain in human subjects. Chronic musculoskeletal pain is prevalent in our society, and constitutes a tremendous public health burden. Although preclinical models of neuropathic and inflammatory pain demonstrate effects on sleep, few studies focus on musculoskeletal pain. We reported elsewhere in this issue of SLEEP that musculoskeletal sensitization alters sleep of mice. In this study we hypothesize that sleep fragmentation during the development of musculoskeletal sensitization will exacerbate subsequent pain responses and alter sleep-wake behavior of mice. Design: This is a preclinical study using C57BL/6J mice to determine the effect on behavioral outcomes of sleep fragmentation combined with musculoskeletal sensitization. Methods: Musculoskeletal sensitization, a model of chronic muscle pain, was induced using two unilateral injections of acidified saline (pH 4.0) into the gastrocnemius muscle, spaced 5 days apart. Musculoskeletal sensitization manifests as mechanical hypersensitivity determined by von Frey filament testing at the hindpaws. Sleep fragmentation took place during the consecutive 12-h light periods of the 5 days between intramuscular injections. Electroencephalogram (EEG) and body temperature were recorded from some mice at baseline and for 3 weeks after musculoskeletal sensitization. Mechanical hypersensitivity was determined at preinjection baseline and on days 1, 3, 7, 14, and 21 after sensitization. Two additional experiments were conducted to determine the independent effects of sleep fragmentation or musculoskeletal sensitization on mechanical hypersensitivity. Results: Five days of sleep fragmentation alone did not induce mechanical hypersensitivity, whereas sleep fragmentation combined with musculoskeletal sensitization resulted in prolonged and exacerbated mechanical hypersensitivity. Sleep fragmentation combined with musculoskeletal sensitization had an effect on subsequent sleep of mice as demonstrated by increased numbers of sleep-wake state transitions during the light and dark periods; changes in nonrapid eye movement (NREM) sleep, rapid eye movement sleep, and wakefulness; and altered delta power during NREM sleep. These effects persisted for at least 3 weeks postsensitization. Conclusions: Our data demonstrate that sleep fragmentation combined with musculoskeletal sensitization exacerbates the physiological and behavioral responses of mice to musculoskeletal sensitization, including mechanical hypersensitivity and sleep-wake behavior. These data contribute to increasing literature demonstrating bidirectional relationships between sleep and pain. The prevalence and incidence of insufficient sleep and pathologies characterized by chronic musculoskeletal pain are increasing in the United States. These demographic data underscore the need for research focused on insufficient sleep and chronic pain so that the quality of life for the millions of individuals with these conditions may be improved. Citation: Sutton BC; Opp MR. Sleep fragmentation exacerbates mechanical hypersensitivity and alters subsequent sleep-wake behavior in a mouse model of musculoskeletal sensitization. SLEEP 2014;37(3):515-524. PMID:24587574

Neural mechanisms underlying urgent and evaluative behaviors: An fMRI study on the interaction of automatic and controlled processes.

PubMed

Megías, Alberto; Navas, Juan Francisco; Petrova, Dafina; Cándido, Antonio; Maldonado, Antonio; Garcia-Retamero, Rocio; Catena, Andrés

2015-08-01

Dual-process theories have dominated the study of risk perception and risk-taking over the last two decades. However, there is a lack of objective brain-level evidence supporting the two systems of processing in every-day risky behavior. To address this issue, we propose the dissociation between evaluative and urgent behaviors as evidence of dual processing in risky driving situations. Our findings show a dissociation of evaluative and urgent behavior both at the behavioral and neural level. fMRI data showed an increase of activation in areas implicated in motor programming, emotional processing, and visuomotor integration in urgent behavior compared to evaluative behavior. These results support a more automatic processing of risk in urgent tasks, relying mainly on heuristics and experiential appraisal. The urgent task, which is characterized by strong time pressure and the possibility for negative consequences among others factors, creates a suitable context for the experiential-affective system to guide the decision-making process. Moreover, we observed greater frontal activation in the urgent task, suggesting the participation of cognitive control in safe behaviors. The findings of this research are relevant for the study of the neural mechanisms underlying dual process models in risky perception and decision-making, especially because of their proximity to everyday activities. © 2015 Wiley Periodicals, Inc.

Behavioral and neurogenomic transcriptome changes in wild-derived zebrafish with fluoxetine treatment

PubMed Central

2013-01-01

Background Stress and anxiety-related behaviors are seen in many organisms. Studies have shown that in humans and other animals, treatment with selective serotonin reuptake inhibitors (e.g. fluoxetine) can reduce anxiety and anxiety-related behaviors. The efficacies and side effects, however, can vary between individuals. Fluoxetine can modulate anxiety in a stereospecific manner or with equal efficacy regardless of stereoisomer depending on the mechanism of action (e.g. serotonergic or GABAergic effects). Zebrafish are an emerging and valuable translational model for understanding human health related issues such as anxiety. In this study we present data showing the behavioral and whole brain transcriptome changes with fluoxetine treatment in wild-derived zebrafish and suggest additional molecular mechanisms of this widely-prescribed drug. Results We used automated behavioral analyses to assess the effects of racemic and stereoisomeric fluoxetine on male wild-derived zebrafish. Both racemic and the individual isomers of fluoxetine reduced anxiety-related behaviors relative to controls and we did not observe stereospecific fluoxetine effects. Using RNA-sequencing of the whole brain, we identified 411 genes showing differential expression with racemic fluoxetine treatment. Several neuropeptides (neuropeptide Y, isotocin, urocortin 3, prolactin) showed consistent expression patterns with the alleviation of stress and anxiety when anxiety-related behavior was reduced with fluoxetine treatment. With gene ontology and KEGG pathway analyses, we identified lipid and amino acid metabolic processes, and steroid biosynthesis among other terms to be over-enriched. Conclusion Our results demonstrate that fluoxetine reduces anxiety-related behaviors in wild-derived zebrafish and alters their neurogenomic state. We identify two biological processes, lipid and amino acid metabolic synthesis that characterize differences in the fluoxetine treated fish. Fluoxetine may be acting on several different molecular pathways to reduce anxiety-related behaviors in wild-derived zebrafish. This study provides data that could help identify common molecular mechanisms of fluoxetine action across animal taxa. PMID:23706039

Impact of head and neck radiotherapy on the mechanical behavior of composite resins and adhesive systems: A systematic review.

PubMed

Madrid Troconis, Cristhian Camilo; Santos-Silva, Alan Roger; Brandão, Thaís Bianca; Lopes, Marcio Ajudarte; de Goes, Mario Fernando

2017-11-01

To analyze the evidence regarding the impact of head and neck radiotherapy (HNRT) on the mechanical behavior of composite resins and adhesive systems. Searches were conducted on PubMed, Embase, Scopus and ISI Web of Science databases using "Radiotherapy", "Composite resins" and "Adhesive systems" as keywords. Selected studies were written in English and assessed the mechanical behavior of composite resins and/or adhesive systems when bonding procedure was conducted before and/or after a maximum radiation dose ≥50Gy, applied under in vitro or in vivo conditions. In total, 115 studies were found but only 16 were included, from which five evaluated the effect of in vitro HNRT on microhardness, wear resistance, diametral tensile and flexural strength of composite resins, showing no significant negative effect in most of reports. Regarding bond strength of adhesive systems, 11 studies were included from which five reported no meaningful negative effect when bonding procedure was conducted before simulated HNRT. Conversely, five studies showed that bond strength diminished when adhesive procedure was done after in vitro radiation therapy. Only two studies about dental adhesion were conducted after in vivo radiotherapy but the results were not conclusive. The mechanical behavior of composite resins and adhesive systems seems not to be affected when in vitro HNRT is applied after bonding procedure. However, bond strength of adhesive systems tends to decrease when simulated radiotherapy is used immediately before bonding procedure. Studies assessing dentin bond strength after in-vivo HNRT were limited and controversial. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Geographic variation in the association between exploratory behavior and physiology in rufous-collared sparrows.

PubMed

Maldonado, Karin; van Dongen, Wouter F D; Vásquez, Rodrigo A; Sabat, Pablo

2012-01-01

Increasing research has attempted to clarify the links between animal personality and physiology. However, the mechanisms driving this association remain largely unknown, and knowledge of how ecological factors may affect its direction and strength is scant. In this study, we quantified variation in the association between exploratory behavior, basal metabolic rate (BMR), and total evaporative water loss (TEWL) in rufous-collared sparrows (Zonotrichia capensis) inhabiting desert, Mediterranean, and cold-temperate climates. We found that the exploratory behavior score was highest in birds from the cold-temperate site, which was characterized by a moderate level of ecological variability (seasonality). Moreover, the association between exploratory behavior and physiological variables differed among localities. Only birds from the Mediterranean site showed a positive correlation between exploratory behavior and BMR. We found no association between exploration and TEWL at any study site. Our findings suggest that differences in the ecological conditions experienced by each sparrow population result in a particular combination of behavioral and physiological traits. An understanding of this intraspecific variation along ecological gradients provides unique insights into how specific ecological conditions affect the coupling of behavioral and physiological traits and the mechanisms underlying that relationship.

Industry Cluster's Adaptive Co-competition Behavior Modeling Inspired by Swarm Intelligence

NASA Astrophysics Data System (ADS)

Xiang, Wei; Ye, Feifan

Adaptation helps the individual enterprise to adjust its behavior to uncertainties in environment and hence determines a healthy growth of both the individuals and the whole industry cluster as well. This paper is focused on the study on co-competition adaptation behavior of industry cluster, which is inspired by swarm intelligence mechanisms. By referencing to ant cooperative transportation and ant foraging behavior and their related swarm intelligence approaches, the cooperative adaptation and competitive adaptation behavior are studied and relevant models are proposed. Those adaptive co-competition behaviors model can be integrated to the multi-agent system of industry cluster to make the industry cluster model more realistic.

Flexural behavior of the fibrous cementitious composites (FCC) containing hybrid fibres

NASA Astrophysics Data System (ADS)

Ramli, Mahyuddin; Ban, Cheah Chee; Samsudin, Muhamad Fadli

2018-02-01

In this study, the flexural behavior of the fibrous cementitious composites containing hybrid fibers was investigated. Waste materials or by product materials such as pulverized fuel ash (PFA) and ground granulated blast-furnace slag (GGBS) was used as supplementary cement replacement. In addition, barchip and kenaf fiber will be used as additional materials for enhance the flexural behavior of cementitious composites. A seven mix design of fibrous cementitious composites containing hybrid fiber mortar were fabricated with PFA-GGBS as cement replacement at 50% with hybridization of barchip and kenaf fiber between 0.5% and 2.0% by total volume weight. The FCC with hybrid fibers mortar will be fabricated by using 50 × 50 × 50 mm, 40 × 40 × 160 mm and 350 × 125 × 30 mm steel mold for assessment of mechanical performances and flexural behavior characteristics. The flexural behavior and mechanical performance of the PFA-GGBS with hybrid fiber mortar block was assessed in terms of load deflection response, stress-strain response, crack development, compressive and flexural strength after water curing for 28 days. Moreover, the specimen HBK 1 and HBK 2 was observed equivalent or better in mechanical performance and flexural behavior as compared to control mortar.

Why bother with the brain? A role for decision neuroscience in understanding strategic variability.

PubMed

Venkatraman, Vinod

2013-01-01

Neuroscience, by its nature, seems to hold considerable promise for understanding the fundamental mechanisms of decision making. In recent years, several studies in the domain of "neuroeconomics" or "decision neuroscience" have provided important insights into brain function. Yet, the apparent success and value of each of these domains are frequently called into question by researchers in economics and behavioral decision making. Critics often charge that knowledge about the brain is unnecessary for understanding decision preferences. In this chapter, I contend that knowledge about underlying brain mechanisms helps in the development of biologically plausible models of behavior, which can then help elucidate the mechanisms underlying individual choice biases and strategic preferences. Using a novel risky choice paradigm, I will demonstrate that people vary in whether they adopt compensatory or noncompensatory rules in economic decision making. Importantly, neuroimaging studies using functional magnetic resonance imaging reveal that distinct neural mechanisms support variability in choices and variability in strategic preferences. Converging evidence from a study involving decisions between hypothetical stocks illustrates how knowledge about the underlying mechanisms can help inform neuroanatomical models of cognitive control. Last, I will demonstrate how knowledge about these underlying neural mechanisms can provide novel insights into the effects of decision states like sleep deprivation on decision preferences. Together, these findings suggest that neuroscience can play a critical role in creating robust and flexible models of real-world decision behavior. Copyright © 2013 Elsevier B.V. All rights reserved.

Data-driven modeling reveals cell behaviors controlling self-organization during Myxococcus xanthus development

PubMed Central

Cotter, Christopher R.; Schüttler, Heinz-Bernd; Igoshin, Oleg A.; Shimkets, Lawrence J.

2017-01-01

Collective cell movement is critical to the emergent properties of many multicellular systems, including microbial self-organization in biofilms, embryogenesis, wound healing, and cancer metastasis. However, even the best-studied systems lack a complete picture of how diverse physical and chemical cues act upon individual cells to ensure coordinated multicellular behavior. Known for its social developmental cycle, the bacterium Myxococcus xanthus uses coordinated movement to generate three-dimensional aggregates called fruiting bodies. Despite extensive progress in identifying genes controlling fruiting body development, cell behaviors and cell–cell communication mechanisms that mediate aggregation are largely unknown. We developed an approach to examine emergent behaviors that couples fluorescent cell tracking with data-driven models. A unique feature of this approach is the ability to identify cell behaviors affecting the observed aggregation dynamics without full knowledge of the underlying biological mechanisms. The fluorescent cell tracking revealed large deviations in the behavior of individual cells. Our modeling method indicated that decreased cell motility inside the aggregates, a biased walk toward aggregate centroids, and alignment among neighboring cells in a radial direction to the nearest aggregate are behaviors that enhance aggregation dynamics. Our modeling method also revealed that aggregation is generally robust to perturbations in these behaviors and identified possible compensatory mechanisms. The resulting approach of directly combining behavior quantification with data-driven simulations can be applied to more complex systems of collective cell movement without prior knowledge of the cellular machinery and behavioral cues. PMID:28533367

A COMBINED EFFECT OF DEXTROMETHORPHAN AND MELATONIN ON NEUROPATHIC PAIN BEHAVIOR IN RATS

PubMed Central

Wang, Shuxing; Zhang, Lin; Lim, Grewo; Sung, Backil; Tian, Yinghong; Chou, Chiu-Wen; Hernstadt, Hayley; Rusanescu, Gabriel; Ma, Yuxin; Mao, Jianren

2009-01-01

Previous study has shown that administration of melatonin into the anterior cingulate cortex contralateral to peripheral nerve injury prevented exacerbation of mechanical allodynia with a concurrent improvement of depression-like behavior in Wistar-Kyoto (WKY) rats, a genetic variation of Wistar rats. In the present study, we examined the effect of the individual versus combined treatment of melatonin and/or dextromethorphan (DM), a clinically available N-methyl-D-aspartate (NMDA) receptor antagonist, on pain behaviors in WKY rats with chronic constriction sciatic nerve injury (CCI). Pain behaviors (thermal hyperalgesia and mechanical allodynia) were established at one week after CCI. WKY rats were then treated intraperitoneally with various doses of melatonin, DM or their combination once daily for the following week. At the end of this one-week treatment, behavioral tests were repeated in these same rats. While DM alone was effective in reducing thermal hyperalgesia at three tested doses (15, 30 or 60 mg/kg), it reduced mechanical allodynia only at high doses (30 or 60 mg/kg). By comparison, administration of melatonin alone was effective in reducing thermal hyperalgesia only at the highest dose (120 mg/kg, but not 30 or 60 mg/kg) tested in this experiment. Melatonin alone failed to reverse allodynia at all three tested doses (30, 60 and 120 mg/kg). However, the combined intraperitoneal administration of melatonin (30 mg/kg) and DM (15 mg/kg) effectively reversed both thermal hyperalgesia and mechanical allodynia although each individual dose alone did not reduce pain behaviors. These results suggest that a combination of melatonin with a clinically available NMDA receptor antagonist might be more effective than either drug alone for the treatment of neuropathic pain. PMID:19595681

A combined effect of dextromethorphan and melatonin on neuropathic pain behavior in rats.

PubMed

Wang, Shuxing; Zhang, Lin; Lim, Grewo; Sung, Backil; Tian, Yinghong; Chou, Chiu-Wen; Hernstadt, Hayley; Rusanescu, Gabriel; Ma, Yuxin; Mao, Jianren

2009-09-08

Previous study has shown that administration of melatonin into the anterior cingulate cortex contralateral to peripheral nerve injury prevented exacerbation of mechanical allodynia with a concurrent improvement of depression-like behavior in Wistar-Kyoto (WKY) rats, a genetic variation of Wistar rats. In the present study, we examined the effect of the individual versus combined treatment of melatonin and/or dextromethorphan (DM), a clinically available N-methyl-d-aspartate (NMDA) receptor antagonist, on pain behaviors in WKY rats with chronic constriction sciatic nerve injury (CCI). Pain behaviors (thermal hyperalgesia and mechanical allodynia) were established at one week after CCI. WKY rats were then treated intraperitoneally with various doses of melatonin, DM or their combination once daily for the following week. At the end of this one-week treatment, behavioral tests were repeated in these same rats. While DM alone was effective in reducing thermal hyperalgesia at three tested doses (15, 30 or 60 mg/kg), it reduced mechanical allodynia only at high doses (30 or 60 mg/kg). By comparison, administration of melatonin alone was effective in reducing thermal hyperalgesia only at the highest dose (120 mg/kg, but not 30 or 60 mg/kg) tested in this experiment. Melatonin alone failed to reverse allodynia at all three tested doses (30, 60 and 120 mg/kg). However, the combined intraperitoneal administration of melatonin (30 mg/kg) and DM (15 mg/kg) effectively reversed both thermal hyperalgesia and mechanical allodynia although each individual dose alone did not reduce pain behaviors. These results suggest that a combination of melatonin with a clinically available NMDA receptor antagonist might be more effective than either drug alone for the treatment of neuropathic pain.

Strain rate dependent hyperelastic stress-stretch behavior of a silica nanoparticle reinforced poly (ethylene glycol) diacrylate nanocomposite hydrogel.

PubMed

Zhan, Yuexing; Pan, Yihui; Chen, Bing; Lu, Jian; Zhong, Zheng; Niu, Xinrui

2017-11-01

Poly (ethylene glycol) diacrylate (PEGDA) derivatives are important biomedical materials. PEGDA based hydrogels have emerged as one of the popular regenerative orthopedic materials. This work aims to study the mechanical behavior of a PEGDA based silica nanoparticle (NP) reinforced nanocomposite (NC) hydrogel at physiological strain rates. The work combines materials fabrication, mechanical experiments, mathematical modeling and structural analysis. The strain rate dependent stress-stretch behaviors were observed, analyzed and quantified. Visco-hyperelasticity was identified as the deformation mechanism of the nano-silica/PEGDA NC hydrogel. NPs showed significant effect on both initial shear modulus and viscoelastic materials properties. A structure-based quasi-linear viscoelastic (QLV) model was constructed and capable to describe the visco-hyperelastic stress-stretch behavior of the NC hydrogel. A group of unified material parameters was extracted by the model from the stress-stretch curves obtained at different strain rates. Visco-hyperelastic behavior of NP/polymer interphase was not only identified but also quantified. The work could provide guidance to the structural design of next-generation NC hydrogel. Copyright © 2017. Published by Elsevier Ltd.

Calcitonin gene-related peptide enhances substance P-induced behaviors via metabolic inhibition: in vivo evidence for a new mechanism of neuromodulation.

PubMed

Mao, J; Coghill, R C; Kellstein, D E; Frenk, H; Mayer, D J

1992-03-06

The present study examined the effects of intrathecal (i.t.) injection of calcitonin gene-related peptide (CGRP) on caudally directed biting and scratching induced by i.t. substance P (SP), bombesin (BBS), strychnine (STR), and kainic acid (KA). CGRP alone (5.25, 10.5 and 21 nmol) had no effect on these behaviors, but CGRP pretreatment produced a dose-related enhancement of behaviors induced by SP or BBS, but not by KA or STR. 2-Amino-5-phosphonovaleric acid (APV, 25 nmol), a selective N-methyl-D-aspartate (NMDA) receptor antagonist, did not block the CGRP potentiation of SP and BBS induced behaviors. CGRP, however, failed to enhance scratching and biting induced by a SP analogue [pGlu5-Mephe8-MeGly9]SP(5-11) (Dime-C7) that is resistant to enzymatic degradation by SP endopeptidase. These findings demonstrate that CGRP potentiates SP induced behavioral responses via inhibition of neuropeptide degradation and that this mechanism may serve as a physiological mechanism of SP modulation.

Simulation of Weld Mechanical Behavior to Include Welding-Induced Residual Stress and Distortion: Coupling of SYSWELD and Abaqus Codes

DTIC Science & Technology

2015-11-01

Memorandum Simulation of Weld Mechanical Behavior to Include Welding -Induced Residual Stress and Distortion: Coupling of SYSWELD and Abaqus Codes... Weld Mechanical Behavior to Include Welding -Induced Residual Stress and Distortion: Coupling of SYSWELD and Abaqus Codes by Charles R. Fisher...TYPE Technical Report 3. DATES COVERED (From - To) Dec 2013 – July 2015 4. TITLE AND SUBTITLE Simulation of Weld Mechanical Behavior to Include

Simulation of Weld Mechanical Behavior to Include Welding Induced Residual Stress and Distortion: Coupling of SYSWELD and Abaqus Codes

DTIC Science & Technology

2015-11-01

Memorandum Simulation of Weld Mechanical Behavior to Include Welding -Induced Residual Stress and Distortion: Coupling of SYSWELD and Abaqus Codes... Weld Mechanical Behavior to Include Welding -Induced Residual Stress and Distortion: Coupling of SYSWELD and Abaqus Codes by Charles R. Fisher...TYPE Technical Report 3. DATES COVERED (From - To) Dec 2013 – July 2015 4. TITLE AND SUBTITLE Simulation of Weld Mechanical Behavior to Include

Does the Incredible Years reduce child externalizing problems through improved parenting? The role of child negative affectivity and serotonin transporter linked polymorphic region (5-HTTLPR) genotype.

PubMed

Weeland, Joyce; Chhangur, Rabia R; Jaffee, Sara R; Van Der Giessen, Danielle; Matthys, Walter; Orobio De Castro, Bram; Overbeek, Geertjan

2018-02-01

In a randomized controlled trial, the Observational Randomized Controlled Trial of Childhood Differential Susceptibility (ORCHIDS study), we tested whether observed parental affect and observed and reported parenting behavior are mechanisms of change underlying the effects of the behavioral parent training program the Incredible Years (IY). Furthermore, we tested whether some children are more susceptible to these change mechanisms because of their temperamental negative affectivity and/or serotonin transporter linked polymorphic region (5-HTTLPR) genotype. Participants were 387 Dutch children between 4 and 8 years of age (M age = 6.31, SD = 1.33; 55.3% boys) and their parents. Results showed that although IY was successful in improving parenting behavior and increasing parental positive affect, these effects did not explain the significant decreases in child externalizing problems. We therefore found no evidence for changes in parenting behavior or parental affect being the putative mechanisms of IY effectiveness. Furthermore, intervention effects on child externalizing behavior were not moderated by child negative affectivity or 5-HTTLPR genotype. However, child 5-HTTLPR genotype did moderate intervention effects on negative parenting behavior. This suggests that in research on behavioral parent training programs, "what works for which parents" might also be an important question.

Psychological entitlement and abusive supervision: political skill as a self-regulatory mechanism.

PubMed

Whitman, Marilyn V; Halbesleben, Jonathon R B; Shanine, Kristen K

2013-01-01

Abusive supervision in the workplace is steadily increasing. Such behavior has been linked to a host of negative individual and organizational consequences. In a health care environment particularly, such behavior can have detrimental effects. This study advances self-regulation theory by framing the entitlement-abusive supervision relationship in terms of a motive to obtain resources via a behavior that is not socially sanctioned. Furthermore, we argue that political skill serves as a self-regulating mechanism that reduces the motivation to secure personal resources through abusive behavior. Our hypotheses were tested using a sample of nurses and their supervisors who were asked to complete a survey. A final sample of 132 supervisor-subordinate dyads was obtained. Analysis suggests that supervisors high in psychological entitlement are more likely to be perceived by their subordinates as abusive. Political skill, however, moderated this relationship by serving as a regulatory mechanism that thwarts entitled supervisors from engaging in abusive behaviors. Our findings underscore the common concern that entitlement and abuse can be harmful for organizations. Entitled supervisors who are high in political skill may recognize that engaging in less aggressive influence behaviors may be more effective in achieving self-serving motives. Consequently, health care organizations need to be proactive in order to reduce entitlement and prevent abusive behaviors in the workplace.

Emotion Dysregulation as a Mechanism Linking Stress Exposure to Adolescent Aggressive Behavior

PubMed Central

McLaughlin, Katie A.; Hatzenbuehler, Mark L.

2012-01-01

Exposure to stress is associated with a wide range of internalizing and externalizing problems in adolescents, including aggressive behavior. Extant research examining mechanisms underlying the associations between stress and youth aggression has consistently identified social information processing pathways that are disrupted by exposure to violence and increase risk of aggressive behavior. In the current study, we use longitudinal data to examine emotion dysregulation as a potential mechanism linking a broader range of stressful experiences to aggressive behavior in a diverse sample of early adolescents (N=1065). Specifically, we examined the longitudinal associations of peer victimization and stressful life events with emotion dysregulation and aggressive behavior. Structural equation modeling was used to create latent constructs of emotion dysregulation and aggression. Both stressful life events and peer victimization predicted subsequent increases in emotion dysregulation over a 4-month period. These increases in emotion dysregulation, in turn, were associated with increases in aggression over the subsequent 3 months. Longitudinal mediation models showed that emotion dysregulation mediated the relationship of both peer victimization (z=2.35, p=0.019) and stressful life events (z=2.32, p=0.020) with aggressive behavior. Increasing the use of adaptive emotion regulation strategies is an important target for interventions aimed at preventing the onset of adolescent aggressive behavior. PMID:22466516

Apollo soil mechanics experiment S-200

NASA Technical Reports Server (NTRS)

Mitchell, J. K.; Houston, W. N.; Carrier, W. D., III; Costes, N. C.

1974-01-01

The physical and mechanical properties of the unconsolidated lunar surface material samples that were obtained during the Apollo missions were studied. Sources of data useful for deduction of soil information, and methods used to obtained the data are indicated. A model for lunar soil behavior is described which considers soil characteristics, density and porosity, strength, compressibility, and trafficability parameters. Lunar history and processes are considered, and a comparison is made of lunar and terrestrial soil behavior. The impact of the findings on future exploration and development of the moon are discussed, and publications resulting from lunar research by the soil mechanics team members are listed.

Academic cheating as a function of defense mechanisms and object relations.

PubMed

Juni, Samuel; Gross, Julie; Sokolowska, Joanna

2006-06-01

This study examined relationships between academic cheating behaviors by using self-reports of past cheating behavior, providing a situational experiment with the opportunity to cheat, and evaluating defense mechanisms and object relations as measured by the Defense Mechanisms Inventory. Subjects included 75 female and 8 male university students ranging in age from 18 to 51 years (M=25.5, SD=6.9). Analysis showed variations in students' self-reported cheating history relative to their measured object relations status and type of defense mechanisms. Actual cheating in the experimental setting was not significantly related to any of these variables. Findings are discussed based on a critique of heterogeneity of the cheating construct.

Behavioral and Neurobiological Mechanisms of Extinction in Pavlovian and Instrumental Learning

PubMed Central

Todd, Travis P.; Vurbic, Drina; Bouton, Mark E.

2013-01-01

This article reviews research on the behavioral and neural mechanisms of extinction as it is represented in both Pavlovian and instrumental learning. In Pavlovian extinction, repeated presentation of a signal without its reinforcer weakens behavior evoked by the signal; in instrumental extinction, repeated occurrence of a voluntary action without its reinforcer weakens the strength of the action. In either case, contemporary research at both the behavioral and neural levels of analysis has been guided by a set of extinction principles that were first generated by research conducted at the behavioral level. The review discusses these principles and illustrates how they have informed the study of both Pavlovian and instrumental extinction. It shows that behavioral and neurobiological research efforts have been tightly linked and that their results are readily integrated. Pavlovian and instrumental extinction are also controlled by compatible behavioral and neural processes. Since many behavioral effects observed in extinction can be multiply determined, we suggest that the current close connection between behavioral-level and neural-level analyses will need to continue. PMID:23999219

Behavioral and neurobiological mechanisms of extinction in Pavlovian and instrumental learning.

PubMed

Todd, Travis P; Vurbic, Drina; Bouton, Mark E

2014-02-01

This article reviews research on the behavioral and neural mechanisms of extinction as it is represented in both Pavlovian and instrumental learning. In Pavlovian extinction, repeated presentation of a signal without its reinforcer weakens behavior evoked by the signal; in instrumental extinction, repeated occurrence of a voluntary action without its reinforcer weakens the strength of the action. In either case, contemporary research at both the behavioral and neural levels of analysis has been guided by a set of extinction principles that were first generated by research conducted at the behavioral level. The review discusses these principles and illustrates how they have informed the study of both Pavlovian and instrumental extinction. It shows that behavioral and neurobiological research efforts have been tightly linked and that their results are readily integrated. Pavlovian and instrumental extinction are also controlled by compatible behavioral and neural processes. Since many behavioral effects observed in extinction can be multiply determined, we suggest that the current close connection between behavioral-level and neural-level analyses will need to continue. Copyright © 2013 Elsevier Inc. All rights reserved.

A Three-Dimensional Computational Model of Collagen Network Mechanics

PubMed Central

Lee, Byoungkoo; Zhou, Xin; Riching, Kristin; Eliceiri, Kevin W.; Keely, Patricia J.; Guelcher, Scott A.; Weaver, Alissa M.; Jiang, Yi

2014-01-01

Extracellular matrix (ECM) strongly influences cellular behaviors, including cell proliferation, adhesion, and particularly migration. In cancer, the rigidity of the stromal collagen environment is thought to control tumor aggressiveness, and collagen alignment has been linked to tumor cell invasion. While the mechanical properties of collagen at both the single fiber scale and the bulk gel scale are quite well studied, how the fiber network responds to local stress or deformation, both structurally and mechanically, is poorly understood. This intermediate scale knowledge is important to understanding cell-ECM interactions and is the focus of this study. We have developed a three-dimensional elastic collagen fiber network model (bead-and-spring model) and studied fiber network behaviors for various biophysical conditions: collagen density, crosslinker strength, crosslinker density, and fiber orientation (random vs. prealigned). We found the best-fit crosslinker parameter values using shear simulation tests in a small strain region. Using this calibrated collagen model, we simulated both shear and tensile tests in a large linear strain region for different network geometry conditions. The results suggest that network geometry is a key determinant of the mechanical properties of the fiber network. We further demonstrated how the fiber network structure and mechanics evolves with a local formation, mimicking the effect of pulling by a pseudopod during cell migration. Our computational fiber network model is a step toward a full biomechanical model of cellular behaviors in various ECM conditions. PMID:25386649

Neuroendocrine control of seasonal plasticity in the auditory and vocal systems of fish

PubMed Central

Forlano, Paul M.; Sisneros, Joseph A.; Rohmann, Kevin N.; Bass, Andrew H.

2014-01-01

Seasonal changes in reproductive-related vocal behavior are widespread among fishes. This review highlights recent studies of the vocal plainfin midshipman fish, Porichthys notatus, a neuroethological model system used for the past two decades to explore neural and endocrine mechanisms of vocal-acoustic social behaviors shared with tetrapods. Integrative approaches combining behavior, neurophysiology, neuropharmacology, neuroanatomy, and gene expression methodologies have taken advantage of simple, stereotyped and easily quantifiable behaviors controlled by discrete neural networks in this model system to enable discoveries such as the first demonstration of adaptive seasonal plasticity in the auditory periphery of a vertebrate as well as rapid steroid and neuropeptide effects on vocal physiology and behavior. This simple model system has now revealed cellular and molecular mechanisms underlying seasonal and steroid-driven auditory and vocal plasticity in the vertebrate brain. PMID:25168757

Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

PubMed Central

Wang, Z.; Georgarakis, K.; Nakayama, K. S.; Li, Y.; Tsarkov, A. A.; Xie, G.; Dudina, D.; Louzguine-Luzgin, D. V.; Yavari, A. R.

2016-01-01

Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses. PMID:27067824

Investigation of the leaching behavior of lead in stabilized/solidified waste using a two-year semi-dynamic leaching test.

PubMed

Xue, Qiang; Wang, Ping; Li, Jiang-Shan; Zhang, Ting-Ting; Wang, Shan-Yong

2017-01-01

Long-term leaching behavior of contaminant from stabilization/solidification (S/S) treated waste stays unclear. For the purpose of studying long-term leaching behavior and leaching mechanism of lead from cement stabilized soil under different pH environment, semi-dynamic leaching test was extended to two years to investigate leaching behaviors of S/S treated lead contaminated soil. Effectiveness of S/S treatment in different scenarios was evaluated by leachability index (LX) and effective diffusion coefficient (D e ). In addition, the long-term leaching mechanism was investigated at different leaching periods. Results showed that no significant difference was observed among the values of the cumulative release of Pb, D e and LX in weakly alkaline and weakly acidic environment (pH value varied from 5.00 to 10.00), and all the controlling leaching mechanisms of the samples immersed in weakly alkaline and weakly acidic environments turned out to be diffusion. Strong acid environment would significantly affect the leaching behavior and leaching mechanism of lead from S/S monolith. The two-year variation of D e appeared to be time dependent, and D e values increased after the 210 th day in weakly alkaline and weakly acidic environment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Neurobiology of aggressive behavior.

PubMed

Delgado, J M

1976-10-30

Causality, neurological mechanisms, and behavioral manifestations may be heterogeneous in different forms of aggressive behavior, but some elements are shared by all forms of violence, including the necessity of sensory inputs, the coding and decoding of information according to acquired frames of reference, and the activation of pre-established patterns of response. Understanding and prevention of violence requires a simultaneous study of its social, cultural, and economic aspects, at parity with an investigation of its neurological mechanisms. Part of the latter information may be obtained through animal experimentation, preferably in non-human primates. Feline predatory behavior has no equivalent in man, and therefore its hypothalamic representation probably does not exist in the human brain. Codes of information, frames of reference for sensory perception, axis to evaluate threats, and formulas for aggressive performance are not established genetically but must be learned individually. We are born with the capacity to learn aggressive behavior, but not with established patterns of violence. Mechanisms for fighting which are acquired by individual experience may be triggered in a similar way by sensory cues, volition, and by electrical stimulation of specific cerebral areas. In monkeys, aggressive responses may be modified by changing the hierarchical position of the stimulated animal, indicating the physiological quality of the neurological mechanisms electrically activated.

Temperature and strain rate dependent behavior of polymer separator for Li-ion batteries

DOE PAGES

Kalnaus, Sergiy; Wang, Yanli; Li, Jianlin; ...

2018-03-07

Safe performance of advanced Li-ion batteries relies on integrity of the separator membrane which prevents contact between electrodes of opposite polarity. Current work provides detailed study of mechanical behavior of such membrane. Temperature and strain rate sensitivity of the triple-layer polypropylene (PP)/polyethylene (PE)/polypropylene (PP) porous separator for Li-ion batteries was studied experimentally under controlled temperatures of up to 120° (393 K), and strain rates (from 1∙10-4s-1 to 0.1s-1). Digital image correlation was used to study strain localization in separator under load. The results show significant dependence of mechanical properties on temperature, with the yield stress decreasing by 30% and elasticmore » modulus decreasing by a factor of two when the temperature is increased from 20 °C to 50 °C. The strain rate strengthening also decreased with higher temperatures while the temperature softening remained independent of the applied strain rate. Application of temperature creates long lasting changes in mechanical behavior of separator as was revealed by performing experiments after the annealing. Such delayed effect of temperature application appears to have directional dependence. The results demonstrate complex behavior of polymer separator which needs to be considered in proper safety assessments of Li-ion batteries.« less

Temperature and strain rate dependent behavior of polymer separator for Li-ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalnaus, Sergiy; Wang, Yanli; Li, Jianlin

Safe performance of advanced Li-ion batteries relies on integrity of the separator membrane which prevents contact between electrodes of opposite polarity. Current work provides detailed study of mechanical behavior of such membrane. Temperature and strain rate sensitivity of the triple-layer polypropylene (PP)/polyethylene (PE)/polypropylene (PP) porous separator for Li-ion batteries was studied experimentally under controlled temperatures of up to 120° (393 K), and strain rates (from 1∙10-4s-1 to 0.1s-1). Digital image correlation was used to study strain localization in separator under load. The results show significant dependence of mechanical properties on temperature, with the yield stress decreasing by 30% and elasticmore » modulus decreasing by a factor of two when the temperature is increased from 20 °C to 50 °C. The strain rate strengthening also decreased with higher temperatures while the temperature softening remained independent of the applied strain rate. Application of temperature creates long lasting changes in mechanical behavior of separator as was revealed by performing experiments after the annealing. Such delayed effect of temperature application appears to have directional dependence. The results demonstrate complex behavior of polymer separator which needs to be considered in proper safety assessments of Li-ion batteries.« less

Behavioral and Metabolic Phenotype Indicate Personality in Zebrafish (Danio rerio).

PubMed

Yuan, Mingzhe; Chen, Yan; Huang, Yingying; Lu, Weiqun

2018-01-01

Consistency of individual differences of animal behavior and personality in reactions to various environmental stresses among their life stages could reflect basic divergences in coping style which may affect survival, social rank, and reproductive success in the wild. However, the physiological mechanisms determining personality remain poorly understood. In order to study whether behavior, metabolism and physiological stress responses relate to the personality, we employed post-stress recovery assays to separate zebrafish into two behavioral types (proactive and reactive). The results demonstrated consistent difference among personality, behavior and metabolism in which proactive individuals were more aggressive, had higher standard metabolic rates and showed lower shuttled frequencies between dark and light compartments than the reactive ones. The behavioral variations were also linked to divergent acute salinity stress responses: proactive individuals adopted a swift locomotion behavior in response to acute salinity challenge while reactive individuals remain unchanged. Our results provide useful insight into how personality acts on correlated traits and the importance of a holistic approach to understanding the mechanisms driving persistent inter-individual differences.

Etazolate rescues behavioral deficits in chronic unpredictable mild stress model: modulation of hypothalamic-pituitary-adrenal axis activity and brain-derived neurotrophic factor level.

PubMed

Jindal, Ankur; Mahesh, Radhakrishnan; Bhatt, Shvetank

2013-11-01

Preliminary study in our laboratory showed that etazolate produced antidepressant- and anxiolytic-like effects in rodent models, however, the ability of etazolate to produce antidepressant- and anxiolytic-like effects and underlying mechanism(s) in chronic unpredictable mild stress (CUMS) model have not been adequately addressed. This study was aimed to investigate the beneficial effects of etazolate on CUMS-induced behavioral deficits (depression- and anxiety-like behaviors). In addition, the possible underlying mechanism(s) of etazolate in CUMS model was also investigated by measuring serum corticosterone (CORT) and brain-derived neurotrophic factor (BDNF) levels. Mice were subjected to a battery of stressors for 28 days. Etazolate (0.5 and 1 mg/kg, p.o.) and fluoxetine (20mg/kg, p.o.) were administered during the last 21 days (8-28th) of the CUMS paradigm. The results showed that 4-weeks CUMS produces significant depression-like behavior in tail suspension test (TST) and partial anxiety-like behavior in elevated plus maze (EPM) and open field test (OFT). Stressed mice have also shown a significant high serum CORT and low BDNF level. Chronic treatment with etazolate (0.5 and 1mg/kg., p.o.) and fluoxetine (20mg/kg., p.o.) produced significant antidepressant-like behavior in TST (decreased duration of immobility), whereas, partial anxiolytic-like behavior in EPM (increased percentage of open arm entries) and OFT (increased % central ambulation score, total ambulation score and time spent in center zone). In addition, etazolate and fluoxetine treatment significantly (p<0.05) increased the BDNF level and inhibited the hypothalamic-pituitary-adrenocortical (HPA) axis hyperactivity, as evidenced by low serum CORT level in stressed mice. In addition, etazolate and fluoxetine also showed significant antidepressant- and anxiolytic-like effects in normal control mice. In this study no significant changes were observed in locomotor activity in actophotometer test. Moreover, we did not find any effect of etazolate and fluoxetine on CORT and BDNF levels in normal control mice. In conclusion, the results of the present study suggested compelling evidences that etazolate has more marked effect on depression-like behavior in mice, which is atleast in part may be related to their modulating effects on the HPA axis and BDNF level. Copyright © 2013 Elsevier Ltd. All rights reserved.

Hierarchically-Driven Approach for Quantifying Fatigue Crack Initiation and Short Crack Growth Behavior in Aerospace Materials

DTIC Science & Technology

2016-08-31

crack initiation and SCG mechanisms (initiation and growth versus resistance). 2. Final summary Here, we present a hierarchical form of multiscale...prismatic faults in -Ti: A combined quantum mechanics /molecular mechanics study 2. Nano-indentation and slip transfer (critical in understanding crack...initiation) 3. An extended-finite element framework (XFEM) to study SCG mechanisms 4. Atomistic methods to develop a grain and twin boundaries database

Olfactory Mechanisms for Discovery of Odorants to Reduce Insect-Host Contact

PubMed Central

Clark, Jonathan T.; Ray, Anandasankar

2016-01-01

Insects have developed highly sophisticated and sensitive olfactory systems to find animal or plant hosts for feeding. Some insects vector pathogens that cause diseases in hundreds of millions of people and destroy billions of dollars of food products every year. There is great interest, therefore, in understanding how the insect olfactory system can be manipulated to reduce their contact with hosts. Here, we review recent advances in our understanding of insect olfactory detection mechanisms, which may serve as a foundation for designing insect control programs based on manipulation of their behaviors by using odorants. Because every insect species has a unique set of olfactory receptors and olfactory-mediated behaviors, we focus primarily on general principles of odor detection that potentially apply to most insects. While these mechanisms have emerged from studies on model systems for study of insect olfaction, such as Drosophila melanogaster, they provide a foundation for discovery of odorants to repel insects or reduce host-seeking behavior. PMID:27628342

Effect of Nb Content on Mechanical Behavior and Structural Properties of W/(Zr55Cu30Al10Ni5)100- x Nb x Composite

NASA Astrophysics Data System (ADS)

Mahmoodan, Morteza; Gholamipour, Reza; Mirdamadi, Shamseddin; Nategh, Said

2017-05-01

In the present study, (Zr55Cu30Al10Ni5)100- x Nb( x=0,1,2,3) bulk metallic glass matrix/tungsten wire composites were fabricated by infiltration process. Structural studies were investigated by scanning electron microscopy and X-ray diffraction method. Also, mechanical behaviors of the materials were analyzed using quasi-static compressive tests. Results indicated that the best mechanical properties i.e., 2105 MPa compressive ultimate strength and 28 pct plastic strain before failure, were achieved in the composite sample with X = 2. It was also found that adding Nb to the matrix modified interface structure in W fiber/(Zr55Cu30Al10Ni5)98Nb2 since the stable diffusion band formation acts as a functionally graded layer. Finally, the observation of multiple shear bands formation in the matrix could confirm the excellent plastic deformation behavior of the composite.

The association of measures of the serotonin system, personality, alcohol use, and smoking with risk-taking traffic behavior in adolescents in a longitudinal study.

PubMed

Luht, Kadi; Eensoo, Diva; Tooding, Liina-Mai; Harro, Jaanus

2018-01-01

Studies on the neurobiological basis of risk-taking behavior have most often focused on the serotonin system. The promoter region of the gene encoding the serotonin transporter contains a polymorphic site (5-HTTLPR) that is important for the transcriptional activity, and studies have demonstrated its association with brain activity and behavior. Another molecular mechanism that reflects the capacity of the central serotonin system is the activity of the enzyme monoamine oxidase (MAO) as measured in platelets. The purpose of the present study was to examine how measures of the serotonin system (platelet MAO activity and the 5-HTTLPR polymorphism), personality variables, alcohol use and smoking are associated with risk-taking traffic behavior in schoolchildren through late adolescence. The younger cohort of the longitudinal Estonian Children Personality Behaviour and Health Study (originally n = 583) filled in questionnaires about personality traits, smoking status, alcohol use and traffic behavior at age 15 and 18 years. From venous blood samples, platelet MAO activity was measured radioenzymatically and 5-HTTLPR was genotyped. During late adolescence, subjects with lower platelet MAO activity were more likely to belong to the high-risk traffic behavior group. Male 5-HTTLPRs'-allele carriers were more likely to belong to the high-risk traffic behavior group compared to the l'/l' homozygotes. Other variables predicting risk group were alcohol use, smoking and Maladaptive impulsivity.The results suggest that lower capacity of the serotoninergic system is associated with more risky traffic behavior during late adolescence, but possibly by different mechanisms in boys and girls.

The Usability of Rock-Like Materials for Numerical Studies on Rocks

NASA Astrophysics Data System (ADS)

Zengin, Enes; Abiddin Erguler, Zeynal

2017-04-01

The approaches of synthetic rock material and mass are widely used by many researchers for understanding the failure behavior of different rocks. In order to model the failure behavior of rock material, researchers take advantageous of different techniques and software. But, the majority of all these instruments are based on distinct element method (DEM). For modeling the failure behavior of rocks, and so to create a fundamental synthetic rock material model, it is required to perform related laboratory experiments for providing strength parameters. In modelling studies, model calibration processes are performed by using parameters of intact rocks such as porosity, grain size, modulus of elasticity and Poisson ratio. In some cases, it can be difficult or even impossible to acquire representative rock samples for laboratory experiments from heavily jointed rock masses and vuggy rocks. Considering this limitation, in this study, it was aimed to investigate the applicability of rock-like material (e.g. concrete) to understand and model the failure behavior of rock materials having complex inherent structures. For this purpose, concrete samples having a mixture of %65 cement dust and %35 water were utilized. Accordingly, intact concrete samples representing rocks were prepared in laboratory conditions and their physical properties such as porosity, pore size and density etc. were determined. In addition, to acquire the mechanical parameters of concrete samples, uniaxial compressive strength (UCS) tests were also performed by simultaneously measuring strain during testing. The measured physical and mechanical properties of these extracted concrete samples were used to create synthetic material and then uniaxial compressive tests were modeled and performed by using two dimensional discontinuum program known as Particle Flow Code (PFC2D). After modeling studies in PFC2D, approximately similar failure mechanism and testing results were achieved from both experimental and artificial simulations. The results obtained from these laboratory tests and modelling studies were compared with the other researcher's studies in respect to failure mechanism of different type of rocks. It can be concluded that there is similar failure mechanism between concrete and rock materials. Therefore, the results obtained from concrete samples that would be prepared at different porosity and pore sizes can be used in future studies in selection micro-mechanical and physical properties to constitute synthetic rock materials for understanding failure mechanism of rocks having complex inherent structures such as vuggy rocks or heavily jointed rock masses.

Microstructure and Mechanical Behavior of 17-4 Precipitation Hardenable Steel Processed by Selective Laser Melting

NASA Astrophysics Data System (ADS)

Rafi, H. Khalid; Pal, Deepankar; Patil, Nachiket; Starr, Thomas L.; Stucker, Brent E.

2014-12-01

The mechanical behavior and the microstructural evolution of 17-4 precipitation hardenable (PH) stainless steel processed using selective laser melting have been studied. Test coupons were produced from 17-4 PH stainless steel powder in argon and nitrogen atmospheres. Characterization studies were carried out using mechanical testing, optical microscopy, scanning electron microscopy, and x-ray diffraction. The results show that post-process heat treatment is required to obtain typically desired tensile properties. Columnar grains of smaller diameters (<2 µm) emerged within the melt pool with a mixture of martensite and retained austenite phases. It was found that the phase content of the samples is greatly influenced by the powder chemistry, processing environment, and grain diameter.

Literature Review and Annotated Bibliography: Water Requirements of Desert Ungulates

USGS Publications Warehouse

Cain, James W.; Krausman, Paul R.; Rosenstock, Steven S.; Turner, Jack C.

2005-01-01

Executive Summary Ungulates adapted to desert areas are able to survive extreme temperatures and limited water availability. This ability is largely due to behavioral, morphological, and physiological adaptations that allow these animals to avoid or tolerate extreme environmental conditions. The physiological adaptations possessed by ungulates for thermoregulation and maintenance of water balance have been the subject of numerous studies involving a wide range of species. In this report we review the behavioral, morphological, and physiological mechanisms used by ungulates and other desert mammals to maintain water and temperature balance in arid environments. We also review some of the more commonly used methods for studying the physiological mechanisms involved in water balance and thermoregulation, and the influence of dehydration on these mechanisms.

Brain and Adrenal Metabolic Responses to Stress (The Role of Brain Catecholamines in Regulation of Response to Stress).

DTIC Science & Technology

1982-03-15

gland was studied in stress states with the finding that there were delayed effects of cold stress*1 on key enzymes effecting the ability to form...phosphorylation. A series of studies were conducted of the effects of various drugs on aggressive behavior. Isolation housing was shown to alter cyclic AMP...mechanisms in the brain. Social behavior was studied in relation to drugs and the effects of amphetamine in relation to paranoid behavior demonstrated using a

Elucidating the mechanisms linking early pubertal timing, sexual activity, and substance use for maltreated versus nonmaltreated adolescents

PubMed Central

Negriff, Sonya; Brensilver, Matthew; Trickett, Penelope K.

2015-01-01

Purpose To test models linking pubertal timing, peer substance use, sexual behavior, and substance use for maltreated versus comparison adolescents. Three theoretical mechanisms were tested: 1) peer influence links early pubertal timing to later sexual behavior and substance use, 2) early maturers engage in substance use on their own and then select substance-using friends, or 3) early maturers initiate sexual behaviors which leads them to substance-using peers. Methods The data came from a longitudinal study of the effects of child maltreatment on adolescent development (303 maltreated and 151 comparison adolescents; age: 9–13 years at initial wave). Multiple-group structural equation models tested the hypotheses across three timepoints including variables of pubertal timing, perception of peer substance use, sexual behavior, and self-reported substance use. Results Early pubertal timing was associated with substance-using peers only for maltreated adolescents, indicating the mediation path from early pubertal timing through substance-using peers to subsequent adolescent substance use and sexual behavior only holds for maltreated adolescents. Mediation via sexual behavior was significant for both maltreated and comparison adolescents. This indicates that sexual behavior may be a more universal mechanism linking early maturation with risky friends regardless of adverse life experiences. Conclusions The findings are a step toward elucidating the developmental pathways from early puberty to risk behavior and identifying early experiences that may alter mediation effects. PMID:26003577

Parental Rearing Behavior Prospectively Predicts Adolescents' Risky Decision-Making and Feedback-Related Electrical Brain Activity

ERIC Educational Resources Information Center

Euser, Anja S.; Evans, Brittany E.; Greaves-Lord, Kirstin; Huizink, Anja C.; Franken, Ingmar H. A.

2013-01-01

The present study examined the role of parental rearing behavior in adolescents' risky decision-making and the brain's feedback processing mechanisms. Healthy adolescent participants ("n" = 110) completed the EMBU-C, a self-report questionnaire on perceived parental rearing behaviors between 2006 and 2008 (T1). Subsequently, after an…

The Efficacy of Conjoint Behavioral Consultation in the Home Setting: Outcomes and Mechanisms in Rural Communities

ERIC Educational Resources Information Center

Sheridan, Susan M.; Witte, Amanda L.; Holmes, Shannon; Wu, ChaoRong; Bhatia, Sonya A.; Angell, Samantha

2017-01-01

This study reports the results of a randomized controlled trial examining the effect of Conjoint Behavioral Consultation (CBC), a family-school partnership intervention, on children's behaviors, parents' skills, and parent-teacher relationships in rural community and town settings. Participants were 267 children, 267 parents, and 152 teachers in…

Exploration of mechanisms underlying the strain-rate-dependent mechanical property of single chondrocytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Trung Dung; Gu, YuanTong, E-mail: yuantong.gu@qut.edu.au

2014-05-05

Based on the characterization by Atomic Force Microscopy, we report that the mechanical property of single chondrocytes has dependency on the strain-rates. By comparing the mechanical deformation responses and the Young's moduli of living and fixed chondrocytes at four different strain-rates, we explore the deformation mechanisms underlying this dependency property. We found that the strain-rate-dependent mechanical property of living cells is governed by both of the cellular cytoskeleton and the intracellular fluid when the fixed chondrocytes are mainly governed by their intracellular fluid, which is called the consolidation-dependent deformation behavior. Finally, we report that the porohyperelastic constitutive material model whichmore » can capture the consolidation-dependent behavior of both living and fixed chondrocytes is a potential candidature to study living cell biomechanics.« less

Can knowledge of developmental processes illuminate the evolution of parental care?

PubMed

Michel, George F; Tyler, Amber N

2007-01-01

There are two levels of investigation for elucidating the evolution of parental behavior. The macro level focuses on how parental behavior can evolve as an aspect of reproduction. The micro level focuses on how species variations in parental behavior evolve. Recently, modern evolutionary biology has turned to developmental biology as a source for information about how trait variability (the substrate upon which natural selection and other evolutionary mechanisms can operate) can emerge during development (called "evo-devo"). Application of this evo-devo approach to the phenomenon of parental behavior requires identification of those mechanisms that produce variations in developmental pathways leading to parental behavior. It is these variations that provide the phenotypes for the potential evolution of different parental behavior systems. Variations in rodent maternal behavior affect the development of the HPA and HPG axes in their offspring. These mechanisms are examined to reveal how such developmental variations could underlie the evolution of biparental behavior. Knowledge of the developmental mechanisms responsible for species variations in mammalian parental behavior systems may provide insight into those mechanisms that may have been involved in the evolution of parental behavior itself. Copyright (c) 2006 Wiley Periodicals, Inc.

Anisotropic constitutive model incorporating multiple damage mechanisms for multiscale simulation of dental enamel.

PubMed

Ma, Songyun; Scheider, Ingo; Bargmann, Swantje

2016-09-01

An anisotropic constitutive model is proposed in the framework of finite deformation to capture several damage mechanisms occurring in the microstructure of dental enamel, a hierarchical bio-composite. It provides the basis for a homogenization approach for an efficient multiscale (in this case: multiple hierarchy levels) investigation of the deformation and damage behavior. The influence of tension-compression asymmetry and fiber-matrix interaction on the nonlinear deformation behavior of dental enamel is studied by 3D micromechanical simulations under different loading conditions and fiber lengths. The complex deformation behavior and the characteristics and interaction of three damage mechanisms in the damage process of enamel are well captured. The proposed constitutive model incorporating anisotropic damage is applied to the first hierarchical level of dental enamel and validated by experimental results. The effect of the fiber orientation on the damage behavior and compressive strength is studied by comparing micro-pillar experiments of dental enamel at the first hierarchical level in multiple directions of fiber orientation. A very good agreement between computational and experimental results is found for the damage evolution process of dental enamel. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Tissue Anisotropy Modeling Using Soft Composite Materials.

PubMed

Chanda, Arnab; Callaway, Christian

2018-01-01

Soft tissues in general exhibit anisotropic mechanical behavior, which varies in three dimensions based on the location of the tissue in the body. In the past, there have been few attempts to numerically model tissue anisotropy using composite-based formulations (involving fibers embedded within a matrix material). However, so far, tissue anisotropy has not been modeled experimentally. In the current work, novel elastomer-based soft composite materials were developed in the form of experimental test coupons, to model the macroscopic anisotropy in tissue mechanical properties. A soft elastomer matrix was fabricated, and fibers made of a stiffer elastomer material were embedded within the matrix material to generate the test coupons. The coupons were tested on a mechanical testing machine, and the resulting stress-versus-stretch responses were studied. The fiber volume fraction (FVF), fiber spacing, and orientations were varied to estimate the changes in the mechanical responses. The mechanical behavior of the soft composites was characterized using hyperelastic material models such as Mooney-Rivlin's, Humphrey's, and Veronda-Westmann's model and also compared with the anisotropic mechanical behavior of the human skin, pelvic tissues, and brain tissues. This work lays the foundation for the experimental modelling of tissue anisotropy, which combined with microscopic studies on tissues can lead to refinements in the simulation of localized fiber distribution and orientations, and enable the development of biofidelic anisotropic tissue phantom materials for various tissue engineering and testing applications.

Tissue Anisotropy Modeling Using Soft Composite Materials

PubMed Central

Callaway, Christian

2018-01-01

Soft tissues in general exhibit anisotropic mechanical behavior, which varies in three dimensions based on the location of the tissue in the body. In the past, there have been few attempts to numerically model tissue anisotropy using composite-based formulations (involving fibers embedded within a matrix material). However, so far, tissue anisotropy has not been modeled experimentally. In the current work, novel elastomer-based soft composite materials were developed in the form of experimental test coupons, to model the macroscopic anisotropy in tissue mechanical properties. A soft elastomer matrix was fabricated, and fibers made of a stiffer elastomer material were embedded within the matrix material to generate the test coupons. The coupons were tested on a mechanical testing machine, and the resulting stress-versus-stretch responses were studied. The fiber volume fraction (FVF), fiber spacing, and orientations were varied to estimate the changes in the mechanical responses. The mechanical behavior of the soft composites was characterized using hyperelastic material models such as Mooney-Rivlin's, Humphrey's, and Veronda-Westmann's model and also compared with the anisotropic mechanical behavior of the human skin, pelvic tissues, and brain tissues. This work lays the foundation for the experimental modelling of tissue anisotropy, which combined with microscopic studies on tissues can lead to refinements in the simulation of localized fiber distribution and orientations, and enable the development of biofidelic anisotropic tissue phantom materials for various tissue engineering and testing applications. PMID:29853996

QUANTUM MECHANICAL STUDY OF THE COMPETITIVE HYDRATION BETWEEN PROTONATED QUINAZOLINE AND LI+, NA+, AND CA2+ IONS

EPA Science Inventory

Hydration reactions are fundamental to many biological functions and environmental processes. The energetics of hydration of inorganic and organic chemical species influences their fate and transport behavior in the environment. In this study, gas-phase quantum mechanical calcula...

The Role of Religiosity in the Relationship between Parents, Peers, and Adolescent Risky Sexual Behavior

ERIC Educational Resources Information Center

Landor, Antoinette; Simons, Leslie Gordon; Simons, Ronald L.; Brody, Gene H.; Gibbons, Frederick X.

2011-01-01

Research has documented a negative relationship between religion and risky sexual behavior. Few studies, however, have examined the processes whereby religion exerts this effect. The present study develops and tests a model of various mechanisms whereby parental religiosity reduces the likelihood of adolescents' participation in risky sexual…

Urban Adolescents' Exercise Intentions and Behaviors: An Exploratory Study of a Trans-Contextual Model

ERIC Educational Resources Information Center

Shen, Bo; McCaughtry, Nate; Martin, Jeffrey

2008-01-01

Using a multi-theory approach, the current study was designed to identify gender differences in the psychological mechanisms by which urban adolescents' motivation in physical education transfers into their leisure-time activities. The theoretical frameworks of Self-Determination Theory and the Theory of Planned Behavior were integrated to…

Mechanical Behavior of Dowel-Type Joints Made of Wood Scrimber Composite

PubMed Central

He, Minjuan; Tao, Duo; Li, Zheng; Li, Maolin

2016-01-01

As a renewable building material with low embodied energy characteristics, wood has gained more and more attention in the green and sustainable building industry. In terms of material resource and physical properties, scrimber composite not only makes full use of fast-growing wood species, but also has better mechanical performance and less inherent variability than natural wood material. In this study, the mechanical behavior of bolted beam-to-column joints built with a kind of scrimber composite was investigated both experimentally and numerically. Two groups of specimens were tested under monotonic and low frequency cyclic loading protocols. The experimental results showed that the bolted joints built with scrimber composite performed well in initial stiffness, ductility, and energy dissipation. A three-dimensional (3D) non-linear finite element model (FEM) for the bolted beam-to-column joints was then developed and validated by experimental results. The validated model was further used to investigate the failure mechanism of the bolted joints through stress analysis. This study can contribute to the application of the proposed scrimber composite in structural engineering, and the developed FEM can serve as a useful tool to evaluate the mechanical behavior of such bolted beam-to-column joints with different configurations in future research. PMID:28773703

Mechanical Behavior of Dowel-Type Joints Made of Wood Scrimber Composite.

PubMed

He, Minjuan; Tao, Duo; Li, Zheng; Li, Maolin

2016-07-15

As a renewable building material with low embodied energy characteristics, wood has gained more and more attention in the green and sustainable building industry. In terms of material resource and physical properties, scrimber composite not only makes full use of fast-growing wood species, but also has better mechanical performance and less inherent variability than natural wood material. In this study, the mechanical behavior of bolted beam-to-column joints built with a kind of scrimber composite was investigated both experimentally and numerically. Two groups of specimens were tested under monotonic and low frequency cyclic loading protocols. The experimental results showed that the bolted joints built with scrimber composite performed well in initial stiffness, ductility, and energy dissipation. A three-dimensional (3D) non-linear finite element model (FEM) for the bolted beam-to-column joints was then developed and validated by experimental results. The validated model was further used to investigate the failure mechanism of the bolted joints through stress analysis. This study can contribute to the application of the proposed scrimber composite in structural engineering, and the developed FEM can serve as a useful tool to evaluate the mechanical behavior of such bolted beam-to-column joints with different configurations in future research.

Children's Intent Attributions and Feelings of Distress: Associations with Maternal and Paternal Parenting Practices

ERIC Educational Resources Information Center

Nelson, David A.; Coyne, Sarah M.

2009-01-01

Many studies point to the importance of social information processing mechanisms in understanding distinct child behaviors such as aggression. However, few studies have assessed whether parenting might be related to such mechanisms. This study considers how aversive forms of parenting (i.e., corporal punishment, psychological control) as well as…

Biological basis of suicide and suicidal behavior

PubMed Central

Pandey, Ghanshyam N

2013-01-01

Objective Suicide is a major public health concern as each year 30,000 people die by suicide in the US alone. In the teenage population, it is the second leading cause of death. There have been extensive studies of psychosocial factors associated with suicide and suicidal behavior. However, very little is known about the neurobiology of suicide. Recent research has provided some understanding of the neurobiology of suicide, which is the topic of this review. Methods Neurobiology of suicide has been studied using peripheral tissues, such as platelets, lymphocytes, and cerebral spinal fluid obtained from suicidal patients or from the postmortem brains of suicide victims. Results These studies have provided encouraging information with regard to the neurobiology of suicide. They show an abnormality of serotonergic mechanism, such as increased serotonin receptor subtypes and decreased serotonin metabolites, such as 5-hydroxyindoleacetic acid. These studies also suggest abnormalities of receptor-linked signaling mechanisms, such as phosphoinositide and adenylyl cyclase signaling mechanisms. Other biological systems that appear to be dysregulated in suicide are the hypothalamic-pituitary-adrenal (HPA) axis, and abnormalities of neurotrophins and neurotrophin receptors. More recently, several studies also indicate abnormalities of neuroimmune functions in suicide. Conclusions These studies have been discussed in detail in the following review. Some encouraging information has emerged, primarily related to some of these neurobiological mechanisms. It is hoped that neurobiological studies may eventually result in identifying appropriate biomarkers for suicidal behavior as well as appropriate therapeutic targets for its treatment. PMID:23773657

Recent advances in behavioral addiction treatments: focusing on mechanisms of change.

PubMed

Longabaugh, Richard; Magill, Molly

2011-10-01

In the latter half of the 20th century, research on behavioral treatments for addictions aimed to develop and test effective treatments. Among the treatments found to be at least moderately effective, direct comparisons failed to reveal consistent superiority of one approach over another. This ubiquitous finding held true despite underlying theories that differed markedly in their proposed causal processes related to patient change. In the 21st century, the focus of treatment research is increasingly on how treatment works for whom rather than whether it works. Studies of active treatment ingredients and mechanisms of behavioral change, while promising, have yielded inconsistent results. Simple mediation analysis may need to be expanded via inclusion of models testing for moderated mediation, mediated moderation, and conditional indirect effects. Examples are offered as to how these more complex models can lead to increased understanding of the conditions under which specific treatment interventions will be effective and mechanisms of change operative in improving behavioral treatments for addictions.

New tricks by an old dogma: mechanisms of the Organizational/Activational Hypothesis of steroid-mediated sexual differentiation of brain and behavior.

PubMed

McCarthy, Margaret M; Wright, Christopher L; Schwarz, Jaclyn M

2009-05-01

The hormonal regulation of sexual behavior has been the topic of study for over 50 years and yet controversies persist regarding the importance of early versus late events and the identity of the critical neural and cellular substrates. We have taken a mechanistic approach toward the masculinizing actions of the gonadal steroid estradiol, as a means to understand how organization of the neuroarchitechture during a perinatal sensitive period exerts enduring influences on adult behavior. We have identified important roles for prostaglandins, FAK and paxillin, PI3 kinase and glutamate, and determined that cell-to-cell signaling is a critical component of the early organizational events. We have further determined that the mechanisms mediating different components of sexual behavior are distinct and regionally specific. The multitude of mechanisms by which the steroid estradiol, exerts divergent effects on the developing nervous system provides for a multitude of phenotypes which can vary significantly both within and between the sexes.

New tricks by an old dogma: Mechanisms of the Organizational/Activational Hypothesis of steroid-mediated sexual differentiation of brain and behavior

PubMed Central

McCarthy, Margaret M.; Wright, Christopher L.; Schwarz, Jaclyn M.

2009-01-01

The hormonal regulation of sexual behavior has been the topic of study for over 50 years and yet controversies persist regarding the importance of early versus late events and the identity of the critical neural and cellular substrates. We have taken a mechanistic approach toward the masculinizing actions of the gonadal steroid estradiol, as a means to understand how organization of the neuroarchitechture during a perinatal sensitive period exerts enduring influences on adult behavior. We have identified important roles for prostaglandins, FAK and paxillin, PI3 kinase and glutamate, and determined that cell-to-cell signaling is a critical component of the early organizational events. We have further determined that the mechanisms mediating different components of sexual behavior are distinct and regionally specific. The multitude of mechanisms by which the steroid estradiol, exerts divergent effects on the developing nervous system provides for a multitude of phenotypes which can vary significantly both within and between the sexes. PMID:19682425

Recent Advances in Behavioral Addiction Treatments: Focusing on Mechanisms of Change

PubMed Central

Longabaugh, Richard; Magill, Molly

2012-01-01

In the latter half of the 20th century, research on behavioral treatments for addictions aimed to develop and test effective treatments. Among treatments found to be at least moderately effective, direct comparisons failed to reveal consistent superiority of one approach over another. This ubiquitous finding held true despite underlying theories that differed markedly in their proposed causal processes related to patient change. In the 21st century the focus of treatment research is increasingly on how treatment works for whom, rather than whether it works. Studies of active treatment ingredients and mechanisms of behavioral change, while promising, have yielded inconsistent results. Simple mediation analysis may need to be expanded by inclusion of models testing for moderated mediation, mediated moderation, and conditional indirect effects. Examples are offered as to how these more complex models can lead to increased understanding of the conditions under which specific treatment interventions will be effective and mechanisms of change operative in improving behavioral treatments for addictions. PMID:21750958

An Examination of Safety and Health Practices in Agricultural Mechanics Education

ERIC Educational Resources Information Center

Threeton, Mark D.; Ewing, John C.

2017-01-01

Providing training of safe operations and behaviors in Agricultural Mechanics classrooms and laboratories is an important aspect of the agricultural education teaching and learning environment. The purpose of this survey research study was to examine current occupational safety and health practices within agricultural mechanics programs. The…

Mechanisms Underlying Sexual Violence Exposure and Psychosocial Sequelae: A Theoretical and Empirical Review

PubMed Central

Walsh, Kate; Galea, Sandro; Koenen, Karestan C.

2015-01-01

Sexual violence is associated with a range of negative mental health and behavioral sequelae, including posttraumatic stress disorder (PTSD), depression, substance abuse/dependence, risky sexual behavior, and interpersonal relationship problems. However, mechanisms underlying these associations are not well understood. Identifying mechanisms that explain linkages between sexual violence and poor outcomes is of paramount importance in determining when and how to intervene to prevent or reduce the magnitude of these outcomes. This review focuses on theories that have been proposed to explain risk of negative outcomes among sexual violence victims, including the development of traumagenic dynamics and emotion dysregulation. We also review promising biological mechanisms that may explain the risk of negative outcomes among sexual violence victims, including studies concerned with epigenetic and neurobiological mechanisms. PMID:25762853

Asymmetrically dominated choice problems, the isolation hypothesis and random incentive mechanisms.

PubMed

Cox, James C; Sadiraj, Vjollca; Schmidt, Ulrich

2014-01-01

This paper presents an experimental study of the random incentive mechanisms which are a standard procedure in economic and psychological experiments. Random incentive mechanisms have several advantages but are incentive-compatible only if responses to the single tasks are independent. This is true if either the independence axiom of expected utility theory or the isolation hypothesis of prospect theory holds. We present a simple test of this in the context of choice under risk. In the baseline (one task) treatment we observe risk behavior in a given choice problem. We show that by integrating a second, asymmetrically dominated choice problem in a random incentive mechanism risk behavior can be manipulated systematically. This implies that the isolation hypothesis is violated and the random incentive mechanism does not elicit true preferences in our example.

A Micro-Level Event-Centered Approach to Investigating Armed Conflict and Population Responses

PubMed Central

Williams, Nathalie E.; Ghimire, Dirgha J.; Axinn, William G.; Jennings, Elyse A.; Pradhan, Meeta S.

2012-01-01

In this article, we construct and test a micro-level event-centered approach to the study of armed conflict and behavioral responses in the general population. Event-centered approaches have been successfully used in the macro-political study of armed conflict but have not yet been adopted in micro-behavioral studies. The micro-level event-centered approach that we advocate here includes decomposition of a conflict into discrete political and violent events, examination of the mechanisms through which they affect behavior, and consideration of differential risks within the population. We focus on two mechanisms: instability and threat of harm. We test this approach empirically in the context of the recent decade-long armed conflict in Nepal, using detailed measurements of conflict-related events and a longitudinal study of first migration, first marriage, and first contraceptive use. Results demonstrate that different conflict-related events independently shaped migration, marriage, and childbearing and that they can simultaneously influence behaviors in opposing directions. We find that violent events increased migration, but political events slowed migration. Both violent and political events increased marriage and contraceptive use net of migration. Overall, this micro-level event-centered approach yields a significant advance for the study of how armed conflict affects civilian behavioral responses. PMID:22911154

Genetic Influences on Adolescent Sexual Behavior: Why Genes Matter for Environmentally-Oriented Researchers

PubMed Central

Harden, K. Paige

2013-01-01

There are dramatic individual differences among adolescents in how and when they become sexually active adults, and “early” sexual activity is frequently cited as a cause of concern for scientists, policymakers, and the general public. Understanding the causes and developmental impact of adolescent sexual activity can be furthered by considering genes as a source of individual differences. Quantitative behavioral genetics (i.e., twin and family studies) and candidate gene association studies now provide clear evidence for the genetic underpinnings of individual differences in adolescent sexual behavior and related phenotypes. Genetic influences on sexual behavior may operate through a variety of direct and indirect mechanisms, including pubertal development, testosterone levels, and dopaminergic systems. Genetic differences may be systematically associated with exposure to environments that are commonly treated as causes of sexual behavior (gene-environment correlation). Possible gene-environment correlations pose a serious challenge for interpreting the results of much behavioral research. Multivariate, genetically-informed research on adolescent sexual behavior compares twins and family members as a form of “quasi-experiment”: How do twins who differ in their sexual experiences differ in their later development? The small but growing body of genetically-informed research has already challenged dominant assumptions regarding the etiology and sequelae of adolescent sexual behavior, with some studies indicating possible positive effects of teenage sexuality. Studies of gene × environment interaction may further elucidate the mechanisms by which genes and environments combine to shape the development of sexual behavior and its psychosocial consequences. Overall, the existence of heritable variation in adolescent sexual behavior has profound implications for environmentally-oriented theory and research. PMID:23855958

The role of descriptive norm within the theory of planned behavior in predicting Korean Americans' exercise behavior.

PubMed

Lee, Hyo

2011-08-01

There are few studies investigating psychosocial mechanisms in Korean Americans' exercise behavior. The present study tested the usefulness of the theory of planned behavior in predicting Korean American's exercise behavior and whether the descriptive norm (i.e., perceptions of what others do) improved the predictive validity of the theory of planned behavior. Using a retrospective design and self-report measures, web-survey responses from 198 Korean-American adults were analyzed using hierarchical regression analyses. The theory of planned behavior constructs accounted for 31% of exercise behavior and 43% of exercise intention. Intention and perceived behavioral control were significant predictors of exercise behavior. Although the descriptive norm did not augment the theory of planned behavior, all original constructs--attitude, injunctive norm (a narrow definition of subjective norm), and perceived behavioral control--statistically significantly predicted leisure-time physical activity intention. Future studies should consider random sampling, prospective design, and objective measures of physical activity.

Prairie Voles as a Model for Understanding the Genetic and Epigenetic Regulation of Attachment Behaviors.

PubMed

Sadino, Julie M; Donaldson, Zoe R

2018-04-06

Over a lifetime, humans build relationships with family, friends, and partners that are critically important for our mental and physical health. Unlike commonly used laboratory mice and rats, Microtine rodents provide a unique model to study the neurobiology underlying pair bonding and the selective attachments that form between adults. Comparisons between monogamous prairie voles and the closely related but nonmonogamous meadow and montane voles have revealed that brain-region-specific neuropeptide receptor patterning modulates social behavior between and within species. In particular, diversity in vasopressin 1a receptor (V1aR) distribution has been linked to individual and species differences in monogamy-related behaviors such as partner preference, mate guarding, and space use. Given the importance of differential receptor expression for regulating social behavior, a critical question has emerged: What are the genetic and epigenetic mechanisms that underlie brain-region-specific receptor patterns? This review will summarize what is known about how the vasopressin (AVP)-V1aR axis regulates social behaviors via signaling in discrete brain regions. From this work, we propose that brain-region-specific regulatory mechanisms facilitate robust evolvability of V1aR expression to generate diverse sociobehavioral traits. Translationally, we provide a perspective on how these studies have contributed to our understanding of human social behaviors and how brain-region-specific regulatory mechanisms might be harnessed for targeted therapies to treat social deficits in psychiatric disorders such as depression, complicated grief, and autism spectrum disorder.

Mechanical response of collagen molecule under hydrostatic compression.

PubMed

Saini, Karanvir; Kumar, Navin

2015-04-01

Proteins like collagen are the basic building blocks of various body tissues (soft and hard). Collagen molecules find their presence in the skeletal system of the body where they bear mechanical loads from different directions, either individually or along with hydroxy-apatite crystals. Therefore, it is very important to understand the mechanical behavior of the collagen molecule which is subjected to multi-axial state of loading. The estimation of strains of collagen molecule along different directions resulting from the changes in hydrostatic pressure magnitude, can provide us new insights into its mechanical behavior. In the present work, full atomistic simulations have been used to study global (volumetric) as well as local (along different directions) mechanical properties of the hydrated collagen molecule which is subjected to different hydrostatic pressure magnitudes. To estimate the local mechanical properties, the strains of collagen molecule along its longitudinal and transverse directions have been acquired at different hydrostatic pressure magnitudes. In spite of non-homogeneous distribution of atoms within the collagen molecule, the calculated values of local mechanical properties have been found to carry the same order of magnitude along the longitudinal and transverse directions. It has been demonstrated that the values of global mechanical properties like compressibility, bulk modulus, etc. as well as local mechanical properties like linear compressibility, linear elastic modulus, etc. are functions of magnitudes of applied hydrostatic pressures. The mechanical characteristics of collagen molecule based on the atomistic model have also been compared with that of the continuum model in the present work. The comparison showed up orthotropic material behavior for the collagen molecule. The information on collagen molecule provided in the present study can be very helpful in designing the future bio-materials. Copyright © 2015 Elsevier B.V. All rights reserved.

Structural and electronic properties of carbon nanotube-reinforced epoxy resins.

PubMed

Suggs, Kelvin; Wang, Xiao-Qian

2010-03-01

Nanocomposites of cured epoxy resin reinforced by single-walled carbon nanotubes exhibit a plethora of interesting behaviors at the molecular level. We have employed a combination of force-field-based molecular mechanics and first-principles calculations to study the corresponding binding and charge-transfer behavior. The simulation study of various nanotube species and curing agent configurations provides insight into the optimal structures in lieu of interfacial stability. An analysis of charge distributions of the epoxy functionalized semiconducting and metallic tubes reveals distinct level hybridizations. The implications of these results for understanding dispersion mechanism and future nano reinforced composite developments are discussed.

Study on mechanical and microstructure behavior of submerged arc welding flux using red mud

NASA Astrophysics Data System (ADS)

Dewangan, Rishi; Pandey, Pankaj K.; Upadhyay, Renu

2018-05-01

This paper emphasis on utilization of Red Mud for preparing submerged arc welding flux and study its mechanical and microstructure behavior. Among the six fluxes prepared in the laboratory, Flux no. 1 (basicity 1.106) found to be best due to its running performance, micro hardness and Brinell hardness. The hardness value (HV) of the fluxes was varying from 165.70 to 217.15 at a load of 1000gm respectively. From the micrograph of welded metal, acicular ferrite found to be optimum which helps in increasing the ductility and hardness of the welded material.

A representative-sandwich model for simultaneously coupled mechanical-electrical-thermal simulation of a lithium-ion cell under quasi-static indentation tests

DOE PAGES

Zhang, Chao; Santhanagopalan, Shriram; Sprague, Michael A.; ...

2015-08-29

The safety behavior of lithium-ion batteries under external mechanical crush is a critical concern, especially during large scale deployment. We previously presented a sequentially coupled mechanical-electrical-thermal modeling approach for studying mechanical abuse induced short circuit. Here in this work, we study different mechanical test conditions and examine the interaction between mechanical failure and electrical-thermal responses, by developing a simultaneous coupled mechanical-electrical-thermal model. The present work utilizes a single representative-sandwich (RS) to model the full pouch cell with explicit representations for each individual component such as the active material, current collector, separator, etc. Anisotropic constitutive material models are presented to describemore » the mechanical properties of active materials and separator. The model predicts accurately the force-strain response and fracture of battery structure, simulates the local failure of separator layer, and captures the onset of short circuit for lithium-ion battery cell under sphere indentation tests with three different diameters. Electrical-thermal responses to the three different indentation tests are elaborated and discussed. Lastly, numerical studies are presented to show the potential impact of test conditions on the electrical-thermal behavior of the cell after the occurrence of short circuit.« less

A representative-sandwich model for simultaneously coupled mechanical-electrical-thermal simulation of a lithium-ion cell under quasi-static indentation tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Chao; Santhanagopalan, Shriram; Sprague, Michael A.

The safety behavior of lithium-ion batteries under external mechanical crush is a critical concern, especially during large scale deployment. We previously presented a sequentially coupled mechanical-electrical-thermal modeling approach for studying mechanical abuse induced short circuit. Here in this work, we study different mechanical test conditions and examine the interaction between mechanical failure and electrical-thermal responses, by developing a simultaneous coupled mechanical-electrical-thermal model. The present work utilizes a single representative-sandwich (RS) to model the full pouch cell with explicit representations for each individual component such as the active material, current collector, separator, etc. Anisotropic constitutive material models are presented to describemore » the mechanical properties of active materials and separator. The model predicts accurately the force-strain response and fracture of battery structure, simulates the local failure of separator layer, and captures the onset of short circuit for lithium-ion battery cell under sphere indentation tests with three different diameters. Electrical-thermal responses to the three different indentation tests are elaborated and discussed. Lastly, numerical studies are presented to show the potential impact of test conditions on the electrical-thermal behavior of the cell after the occurrence of short circuit.« less

Servant leadership and employee voice behavior: a cross-level investigation in China.

PubMed

Yan, Aimin; Xiao, Yigui

2016-01-01

This study tested the influence and mechanisms of servant leadership on voice behavior, including the mediating role of psychological safety, and the moderating role of supervisor-subordinate Guanxi. Data were collected from 430 civil servants and their immediate supervisors in Changsha, China. Cross-Level investigation revealed that servant leadership had a significant influence on voice behavior, psychological safety mediated the relationship between servant leadership and voice behavior, while supervisor-subordinate Guanxi negatively moderated the relationship between servant leadership and voice behavior.

Environmental influences on energy balance-related behaviors: A dual-process view

PubMed Central

Kremers, Stef PJ; de Bruijn, Gert-Jan; Visscher, Tommy LS; van Mechelen, Willem; de Vries, Nanne K; Brug, Johannes

2006-01-01

Background Studies on the impact of the 'obesogenic' environment have often used non-theoretical approaches. In this journal's debate and in other papers authors have argued the necessity of formulating conceptual models for differentiating the causal role of environmental influences on behavior. Discussion The present paper aims to contribute to the debate by presenting a dual-process view on the environment – behavior relationship. This view is conceptualized in the EnRG framework (Environmental Research framework for weight Gain prevention). In the framework, behavior is postulated to be the result of a simultaneous influence of conscious and unconscious processes. Environmental influences are hypothesized to influence behavior both indirectly and directly. The indirect causal mechanism reflects the mediating role of behavior-specific cognitions in the influence of the environment on behavior. A direct influence reflects the automatic, unconscious, influence of the environment on behavior. Specific personal and behavioral factors are postulated to moderate the causal path (i.e., inducing either the automatic or the cognitively mediated environment – behavior relation). In addition, the EnRG framework applies an energy balance-approach, stimulating the integrated study of determinants of diet and physical activity. Conclusion The application of a dual-process view may guide research towards causal mechanisms linking specific environmental features with energy balance-related behaviors in distinct populations. The present paper is hoped to contribute to the evolution of a paradigm that may help to disentangle the role of 'obesogenic' environmental factors. PMID:16700907

What can individual differences reveal about face processing?

PubMed Central

Yovel, Galit; Wilmer, Jeremy B.; Duchaine, Brad

2014-01-01

Faces are probably the most widely studied visual stimulus. Most research on face processing has used a group-mean approach that averages behavioral or neural responses to faces across individuals and treats variance between individuals as noise. However, individual differences in face processing can provide valuable information that complements and extends findings from group-mean studies. Here we demonstrate that studies employing an individual differences approach—examining associations and dissociations across individuals—can answer fundamental questions about the way face processing operates. In particular these studies allow us to associate and dissociate the mechanisms involved in face processing, tie behavioral face processing mechanisms to neural mechanisms, link face processing to broader capacities and quantify developmental influences on face processing. The individual differences approach we illustrate here is a powerful method that should be further explored within the domain of face processing as well as fruitfully applied across the cognitive sciences. PMID:25191241

Microstructural and Morphological Factors Affecting Uncertainty in Small Scale Mechanical Properties

NASA Astrophysics Data System (ADS)

Maughan, Michael R.

If materials are to be developed from the ground up, the process will be dependent upon accurate and well-defined models of material behavior. These models can be closed-form solutions developed from first principles, simulations, or empirically derived equations, among others. Material behavior at the mesoscale is in general well understood, having had several centuries of study. However, behavior at the micro or nanoscale still requires characterization. Understanding the collective influence of the microstructure on the bulk material, for example with models like the Hall-Petch relation, has advanced our ability to manipulate the material to our advantage. We now have the ability to study not only the structure of the material, but also the material behavior and properties at the nanoscale. Understanding this behavior is critical to developing a framework for interpreting and utilizing these properties in materials design. This research aims to improve the fundamental understanding of the mechanical performance of materials and the subsequent variation in measured properties. The literature reports widely varying material properties such as hardness, elastic modulus, and yield point when measured at the nanoscale. Proposed variation mechanisms in these properties include surface preparation, error in measurement, heterogeneous dislocation density and distribution, crystal orientation, surface oxide film fracture, and others. Among other things, this work shows that these sources of variation can be determined and quantified, and that this information can be utilized as a characterization and/or predictive tool. The main goals of this work are to 1) continue basic research on sources of variation in the nanoscale properties of materials, specifically hardness and modulus in crystalline and glassy solids, 2) study the abrupt transition from elastic to plastic material behavior known as pop-in and resolve the problem of pseudo-elastic behavior prior to plasticity, and 3) integrate the sources of and propagate the variation into materials simulations, 4) study the influence of dislocation processes on indentation size effects, and 5) apply this learning to difficult to measure or interpret materials applications.

Sleep Duration and Diabetes Risk: Population Trends and Potential Mechanisms.

PubMed

Grandner, Michael A; Seixas, Azizi; Shetty, Safal; Shenoy, Sundeep

2016-11-01

Sleep is important for regulating many physiologic functions that relate to metabolism. Because of this, there is substantial evidence to suggest that sleep habits and sleep disorders are related to diabetes risk. In specific, insufficient sleep duration and/or sleep restriction in the laboratory, poor sleep quality, and sleep disorders such as insomnia and sleep apnea have all been associated with diabetes risk. This research spans epidemiologic and laboratory studies. Both physiologic mechanisms such as insulin resistance, decreased leptin, and increased ghrelin and inflammation and behavioral mechanisms such as increased food intake, impaired decision-making, and increased likelihood of other behavioral risk factors such as smoking, sedentary behavior, and alcohol use predispose to both diabetes and obesity, which itself is an important diabetes risk factor. This review describes the evidence linking sleep and diabetes risk at the population and laboratory levels.

The mechanism of sound production in túngara frogs and its role in sexual selection and speciation.

PubMed

Ryan, Michael J; Guerra, Mónica A

2014-10-01

Sexual communication can evolve in response to sexual selection, and it can also cause behavioral reproductive isolation between populations and thus drive speciation. Anurans are an excellent system to investigate these links between behavior and evolution because we have detailed knowledge of how neural mechanisms generate behavioral preferences for calls and how these preferences then generate selection on call variation. But we know far less about the physical mechanisms of call production, especially how different laryngeal morphologies generate call variation. Here we review studies of a group of species that differ in the presence of a secondary call component that evolved under sexual selection. We discuss how the larynx produces this call component, and how laryngeal morphology generates sexual selection and can contribute to speciation. Copyright © 2014. Published by Elsevier Ltd.

Levels of behavioral organization and the evolution of division of labor

NASA Astrophysics Data System (ADS)

Page, Robert E.; Erber, Joachim

2002-03-01

The major features of insect societies that fascinate biologists are the self-sacrificing altruism expressed by colony members, the complex division of labor, and the tremendous plasticity demonstrated in the face of changing environments. The social behavior of insects is a result of complex interactions at different levels of biological organization. Genes give rise to proteins and peptides that build the nervous and muscular systems, regulate their own synthesis, interact with each other, and affect the behavior of individuals. Social behavior emerges from the complex interactions of individuals that are themselves far removed from the direct effects of the genes. In order to understand how social organization evolves, we must understand the mechanisms that link the different levels of organization. In this review, we discuss how behavior is influenced by genes and the neural system and how social behavior emerges from the behavioral activities of individuals. We show how different levels of organization share common features and are linked through common mechanisms. We focus on the behavior of the honey bee, the best studied of all social insects.

Physiology of Sedentary Behavior and Its Relationship to Health Outcomes

PubMed Central

Thyfault, John P; Du, Mengmeng; Kraus, William E; Levine, James A; Booth, Frank W

2014-01-01

Purpose This paper reports on the findings and recommendations of the “Physiology of Sedentary Behavior and its Relationship to Health Outcomes” group, a part of a larger workshop entitled Sedentary Behavior: Identifying Research Priorities sponsored by the National Heart, and Lung and Blood Institute and the National Institute on Aging, which aimed to establish sedentary behavior research priorities. Methods The discussion within our workshop lead to the formation of critical physiological research objectives related to sedentary behaviors, that if appropriately researched would greatly impact our overall understanding of human health and longevity. Results and Conclusions Primary questions are related to physiological “health outcomes” including the influence of physical activity vs. sedentary behavior on function of a number of critical physiological systems (aerobic capacity, skeletal muscle metabolism and function, telomeres/genetic stability, and cognitive function). The group also derived important recommendations related to the “central and peripheral mechanisms” that govern sedentary behavior and how energy balance has a role in mediating these processes. General recommendations for future sedentary physiology research efforts include that studies of sedentary behavior, including that of sitting time only, should focus on the physiological impact of a “lack of human movement” in contradistinction to the effects of physical movement and that new models or strategies for studying sedentary behavior induced adaptations and links to disease development are needed to elucidate underlying mechanism(s). PMID:25222820

Nonlinear Viscoelastic Characterization of the Porcine Spinal Cord

PubMed Central

Shetye, Snehal; Troyer, Kevin; Streijger, Femke; Lee, Jae H. T.; Kwon, Brian K.; Cripton, Peter; Puttlitz, Christian M.

2014-01-01

Although quasi-static and quasi-linear viscoelastic properties of the spinal cord have been reported previously, there are no published studies that have investigated the fully (strain-dependent) nonlinear viscoelastic properties of the spinal cord. In this study, stress relaxation experiments and dynamic cycling were performed on six fresh porcine lumbar cord specimens to examine their viscoelastic mechanical properties. The stress relaxation data were fitted to a modified superposition formulation and a novel finite ramp time correction technique was applied. The parameters obtained from this fitting methodology were used to predict the average dynamic cyclic viscoelastic behavior of the porcine cord. The data indicate that the porcine spinal cord exhibited fully nonlinear viscoelastic behavior. The average weighted RMSE for a Heaviside ramp fit was 2.8kPa, which was significantly greater (p < 0.001) than that of the nonlinear (comprehensive viscoelastic characterization (CVC) method) fit (0.365kPa). Further, the nonlinear mechanical parameters obtained were able to accurately predict the dynamic behavior, thus exemplifying the reliability of the obtained nonlinear parameters. These parameters will be important for future studies investigating various damage mechanisms of the spinal cord and studies developing high resolution finite elements models of the spine. PMID:24211612

Effect of Temperature on the Deformation Behavior of B2 Austenite in a Polycrystalline Ni49.9Ti50.1 (at.Percent) Shape Memory Alloy

NASA Technical Reports Server (NTRS)

Garg, A.; Benafan, O.; Noebe, R. D.; Padula, S. A., II; Clausen, B.; Vogel, S.; Vaidyanathan, R.

2013-01-01

Superelasticity in austenitic B2-NiTi is of great technical interest and has been studied in the past by several researchers [1]. However, investigation of temperature dependent deformation in B2-NiTi is equally important since competing mechanisms of stress-induced martensite (SIM), retained martensite, plastic and deformation twinning can lead to unusual mechanical behaviors. Identification of the role of various mechanisms contributing to the overall deformation response of B2-NiTi is imperative to understanding and maturing SMA-enabled technologies. Thus, the objective of this work was to study the deformation of polycrystalline Ni49.9Ti50.1 (at. %) above A(sub f) (105 C) in the B2 state at temperatures between 165-440 C, and generate a B2 deformation map showing active deformation mechanisms in different temperature-stress regimes.

Mechanisms of transgenerational inheritance of addictive-like behaviors.

PubMed

Vassoler, F M; Sadri-Vakili, G

2014-04-04

Genetic factors are implicated in the heritability of drug abuse. However, even with advances in current technology no specific genes have been identified that are critical for the transmission of drug-induced phenotypes to subsequent generations. It is now evident that epigenetic factors contribute to disease heritability and represent a link between genes and the environment. Recently, epigenetic mechanisms have been shown to underlie drug-induced structural, synaptic, and behavioral plasticity by coordinating the expression of gene networks within the brain. Therefore, the epigenome provides a direct mechanism for drugs of abuse to influence the genetic events involved in the development of addiction as well as its heritability to subsequent generations. In this review we discuss the mechanisms underlying intergenerational epigenetic transmission, highlight studies that demonstrate this phenomenon with particular attention to the field of addiction, and identify gaps for future studies. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

On the effect of hydrogen on the mechanical behavior of Beta-C titanium in aged condition

NASA Astrophysics Data System (ADS)

Alvarez, Anna-Maria

The effect of hydrogen in solid solution on the mechanical behavior of the metastable beta-titanium alloy Beta-C was studied. The samples were aged at 482°C for 28 h prior to hydrogen charging in order to obtain a microstructure of alpha-precipitates in a beta-phase matrix. The kinetics and thermodynamics of hydrogen uptake in the alloy were studied in order to determine the required parameters to gas charge the samples with hydrogen, without altering the microstructure. The mechanical samples were hydrogen charged at 350°C to hydrogen concentrations between 0.6 and 24 at%. The samples were thereafter tested under tensile and alternating loading in order to study the effect of hydrogen on the tensile properties, fatigue properties and crack propagation rate. The fracture surfaces were then studied by using SEM, TEM and X-ray diffraction techniques. The macroscopic mechanical properties were compared with the micromechanisms of deformation and fracture in order to obtain information about the operating hydrogen-enhanced fracture mechanism. It was found that the tensile behavior was sensitive to hydrogen. A sharp ductile-to-brittle transition (DBT) occurred when hydrogen in solid solution reached a concentration of about 3.5 at%. TEM and X-ray analysis showed that stress-induced hydrides form in areas of low stress intensities at hydrogen concentrations above the DBT, and it is therefore believed that this is the cause of the hydrogen embrittlement in this alloy. However, at higher stress intensities, slip localization and enhanced slip band fracture were observed. Since slip localization and hydrogen-induced slip band fracture have previously been connected with a large decrease in ductility it can not be excluded that these effects of hydrogen affects the DBT. The cyclic stress strain behavior was not affected by hydrogen; the non-linear elastic behavior and the cyclic softening did not change with introduction of hydrogen up to a level of 10.8 at%. The fatigue life was, however, reduced when hydrogen charged samples were tested at low frequency (0.00032 Hz).

Animal Foraging and the Evolution of Goal-Directed Cognition

ERIC Educational Resources Information Center

Hills, Thomas T.

2006-01-01

Foraging-and feeding-related behaviors across eumetazoans share similar molecular mechanisms, suggesting the early evolution of an optimal foraging behavior called area-restricted search (ARS), involving mechanisms of dopamine and glutamate in the modulation of behavioral focus. Similar mechanisms in the vertebrate basal ganglia control motor…

Spurious heat conduction behavior of finite-size graphene nanoribbon under extreme uniaxial strain caused by the AIREBO potential

NASA Astrophysics Data System (ADS)

Yang, Xueming; Wu, Sihan; Xu, Jiangxin; Cao, Bingyang; To, Albert C.

2018-02-01

Although the AIREBO potential can well describe the mechanical and thermal transport of the carbon nanostructures under normal conditions, previous studies have shown that it may overestimate the simulated mechanical properties of carbon nanostructures in extreme strains near fracture. It is still unknown whether such overestimation would also appear in the thermal transport of nanostructrues. In this paper, the mechanical and thermal transport of graphene nanoribbon under extreme deformation conditions are studied by MD simulations using both the original and modified AIREBO potential. Results show that the cutoff function of the original AIREBO potential produces an overestimation on thermal conductivity in extreme strains near fracture stage. Spurious heat conduction behavior appears, e.g., the thermal conductivity of GNRs does not monotonically decrease with increasing strain, and even shows a ;V; shaped reversed and nonphysical trend. Phonon spectrum analysis show that it also results in an artificial blue shift of G peak and phonon stiffening of the optical phonon modes. The correlation between spurious heat conduction behavior and overestimation of mechanical properties near the fracture stage caused by the original AIREBO potential are explored and revealed.

Effect of cellulose nanocrystals (CNC) on rheological and mechanical properties and crystallization behavior of PLA/CNC nanocomposites.

PubMed

Kamal, Musa R; Khoshkava, Vahid

2015-06-05

In earlier work, we reported that spray freeze drying of cellulose nanocrystals (CNC) yields porous agglomerate structures. On the other hand, the conventional spray dried CNC (CNCSD) and the freeze dried CNC (CNCFD) produce compact solid structures with very low porosity. As it is rather difficult to obtain direct microscopic evidence of the quality of dispersion of CNC in polymer nanocomposites, it was shown that supporting evidence of the quality and influence of dispersion in a polypropylene (PP)/CNC nanocomposite could be obtained by studying the rheological behavior, mechanical properties and crystallization characteristics of PP/CNC nanocomposites. In an effort to produce a sustainable, fully biosourced, biodegradable nanocomposite, this manuscript presents the results of a study of the rheological, mechanical and crystallization behavior of PLA/CNCSFD nanocomposites obtained by melt processing. The results are analyzed to determine CNC network formation, rheological percolation threshold concentrations, mechanical properties in the rubbery and glassy states, and the effect of CNCSFD on crystalline nucleation and crystallization rates of PLA. These results suggest that the porosity and network structure of CNCSFD agglomerates contribute significantly to good dispersion of CNC in the PLA matrix. Copyright © 2015 Elsevier Ltd. All rights reserved.

An application of interactive computer graphics technology to the design of dispersal mechanisms

NASA Technical Reports Server (NTRS)

Richter, B. J.; Welch, B. H.

1977-01-01

Interactive computer graphics technology is combined with a general purpose mechanisms computer code to study the operational behavior of three guided bomb dispersal mechanism designs. These studies illustrate the use of computer graphics techniques to discover operational anomalies, to assess the effectiveness of design improvements, to reduce the time and cost of the modeling effort, and to provide the mechanism designer with a visual understanding of the physical operation of such systems.

Early Childhood Maltreatment and Girls' Sexual Behavior: The Mediating Role of Pubertal Timing.

PubMed

Ryan, Rebecca M; Mendle, Jane; Markowitz, Anna J

2015-09-01

Although links between early childhood maltreatment and girls' sexual behavior in adolescence have been well established, it is unclear whether different forms of maltreatment are differentially associated with sexual outcomes and whether distinct mechanisms explain associations across maltreatment types. Using data from National Longitudinal Study of Adolescent Health (Add Health), the present study examines whether physical abuse, sexual abuse, and physical neglect in early childhood differentially predict girls' age at first intercourse and number of sexual partners in early adulthood. The study also tests whether early pubertal timing mediates the link between early maltreatment and sexual behavior (N = 6,364). Findings indicate that early sexual and physical abuse were equally predictive of earlier age at first intercourse and a greater number of sexual partners, but that only the sexual abuse-age at first intercourse link was mediated by early puberty. These results suggest that sexual abuse and physical abuse are associated with earlier and riskier sexual behavior in girls relative to no maltreatment and to similar degrees. However, only the link between sexual abuse and sexual behavior involves a biological mechanism manifested in early pubertal timing. Copyright © 2015 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

Exposure to chronic variable social stress during adolescence alters affect-related behaviors and adrenocortical activity in adult male and female inbred mice.

PubMed

Caruso, Michael J; Kamens, Helen M; Cavigelli, Sonia A

2017-09-01

Rodent models provide valuable insight into mechanisms that underlie vulnerability to adverse effects of early-life challenges. Few studies have evaluated sex differences in anxiogenic or depressogenic effects of adolescent social stress in a rodent model. Furthermore, adolescent stress studies often use genetically heterogeneous outbred rodents which can lead to variable results. The current study evaluated the effects of adolescent social stress in male and female inbred (BALB/cJ) mice. Adolescent mice were exposed to repeat cycles of alternating social isolation and social novelty for 4 weeks. Adolescent social stress increased anxiety-related behaviors in both sexes and depression-related behavior in females. Locomotion/exploratory behavior was also decreased in both sexes by stress. Previously stressed adult mice produced less basal fecal corticosteroids than controls. Overall, the novel protocol induced sex-specific changes in anxiety- and depression-related behaviors and corticoid production in inbred mice. The chronic variable social stress protocol used here may be beneficial to systematically investigate sex-specific neurobiological mechanisms underlying adolescent stress vulnerability where genetic background can be controlled. © 2017 Wiley Periodicals, Inc.

Chemical Ototoxicity of the Fish Inner Ear and Lateral Line.

PubMed

Coffin, Allison B; Ramcharitar, John

2016-01-01

Hair cell-driven mechanosensory systems are crucial for successful execution of a number of behaviors in fishes, and have emerged as good models for exploring questions relevant to human hearing. This review focuses on ototoxic effects in the inner ear and lateral line system of fishes. We specifically examine studies where chemical ototoxins such as aminoglycoside antibiotics have been employed as tools to disable the lateral line. Lateral line ablation results in alterations to feeding behavior and orientation to water current in a variety of species. However, neither behavior is abolished in the presence of additional sensory cues, supporting the hypothesis that many fish behaviors are driven by multisensory integration. Within biomedical research, the larval zebrafish lateral line has become an important model system for understanding signaling mechanisms that contribute to hair cell death and for developing novel pharmacological therapies that protect hair cells from ototoxic damage. Furthermore, given that fishes robustly regenerate damaged hair cells, ototoxin studies in fishes have broadened our understanding of the molecular and genetic events in an innately regenerative system, offering potential targets for mammalian hair cell regeneration. Collectively, studies of fish mechanosensory systems have yielded insight into fish behavior and in mechanisms of hair cell death, protection, and regeneration.

Dynamic Manipulation of Hydrogels to Control Cell Behavior: A Review

PubMed Central

Vats, Kanika

2013-01-01

For many tissue engineering applications and studies to understand how materials fundamentally affect cellular functions, it is important to have the ability to synthesize biomaterials that can mimic elements of native cell–extracellular matrix interactions. Hydrogels possess many properties that are desirable for studying cell behavior. For example, hydrogels are biocompatible and can be biochemically and mechanically altered by exploiting the presentation of cell adhesive epitopes or by changing hydrogel crosslinking density. To establish physical and biochemical tunability, hydrogels can be engineered to alter their properties upon interaction with external driving forces such as pH, temperature, electric current, as well as exposure to cytocompatible irradiation. Additionally, hydrogels can be engineered to respond to enzymes secreted by cells, such as matrix metalloproteinases and hyaluronidases. This review details different strategies and mechanisms by which biomaterials, specifically hydrogels, can be manipulated dynamically to affect cell behavior. By employing the appropriate combination of stimuli and hydrogel composition and architecture, cell behavior such as adhesion, migration, proliferation, and differentiation can be controlled in real time. This three-dimensional control in cell behavior can help create programmable cell niches that can be useful for fundamental cell studies and in a variety of tissue engineering applications. PMID:23541134

Worker Personality and Its Association with Spatially Structured Division of Labor

PubMed Central

Pamminger, Tobias; Foitzik, Susanne; Kaufmann, Katharina C.; Schützler, Natalie; Menzel, Florian

2014-01-01

Division of labor is a defining characteristic of social insects and fundamental to their ecological success. Many of the numerous tasks essential for the survival of the colony must be performed at a specific location. Consequently, spatial organization is an integral aspect of division of labor. The mechanisms organizing the spatial distribution of workers, separating inside and outside workers without central control, is an essential, but so far neglected aspect of division of labor. In this study, we investigate the behavioral mechanisms governing the spatial distribution of individual workers and its physiological underpinning in the ant Myrmica rubra. By investigating worker personalities we uncover position-associated behavioral syndromes. This context-independent and temporally stable set of correlated behaviors (positive association between movements and attraction towards light) could promote the basic separation between inside (brood tenders) and outside workers (foragers). These position-associated behavior syndromes are coupled with a high probability to perform tasks, located at the defined position, and a characteristic cuticular hydrocarbon profile. We discuss the potentially physiological causes for the observed behavioral syndromes and highlight how the study of animal personalities can provide new insights for the study of division of labor and self-organized processes in general. PMID:24497911

Rheological and mechanical properties of polypropylene prepared with multi-walled carbon nanotube masterbatch.

PubMed

Shim, Young-Sun; Park, Soo-Jin

2012-07-01

In this study, the effects of polypropylene-grafted maleic-anhydride-treated multi-walled carbon nanotubes (PP-MWNTs) on the viscoelastic behaviors and mechanical properties of a polypropylene-(PP)-based composite system were examined. The PP-MWNT/PP composites were prepared via melt mixing with a 3:1 ratio of PP-g-MA and acid-treated MWNTs at 220 degrees C. The surface characteristics of the PP-MWNTs were confirmed via Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). The viscoelastic behavior and mechanical properties of the PP-MWNT/PP composites were confirmed using a rheometer and an ultimate testing machine (UTM). The storage and loss moduli increased with increasing PP-MWNT content. The critical intensity stress factor (K(IC)) of the PP-MWNT/PP composites at high filler loading was also higher than that of the MWNT/PP composites. In conclusion, the viscoelastic behavior and mechanical properties of MWNT/PP can be improved by grafting MWNTs to PP-g-MA.

Exploration of Mechanisms behind Changes after Participation in a Parenting Intervention: A Qualitative Study in a Low-Resource Setting.

PubMed

Mejia, Anilena; Ulph, Fiona; Calam, Rachel

2016-03-01

Parenting interventions are effective for preventing psychological difficulties in children. However, their active ingredients have not been comprehensively explored. How do they work? What are the mechanisms operating behind changes? In 2012, a randomized controlled trial of a parenting intervention was conducted in low-resource communities of Panama. Effects on child behavioral difficulties, parental stress, and parenting practices were large in the short and long term. This was an ideal opportunity to explore potential mechanisms operating behind effects found in this low-resource setting. Twenty-five parents were interviewed. Data were analyzed through an inductive semantic thematic analysis. Three themes emerged from the data: (a) psychological mechanisms behind changes, (b) behavioral changes in parent, and (c) changes in the children. Parents described that the intervention triggered changes in emotion regulation, self-efficacy, and problem solving. Parents also reported behavioral changes such as praising their children more often, who in turn seemed more responsible and better at following instructions. The study offers participant-driven insight into potential pathways of change after participation in this parenting intervention, pathways that are often overlooked in quantitative studies. Future studies should further explore these pathways, through mediator and moderator analyses, and determine how much is shared across interventions and across different cultural settings. © Society for Community Research and Action 2016.

The role of Hydrogen and Creep in Intergranular Stress Corrosion Cracking of Alloy 600 and Alloy 690 in PWR Primary Water Environments ? a Review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rebak, R B; Hua, F H

2004-07-12

Intergranular attack (IGA) and intergranular stress corrosion cracking (IGSCC) of Alloy 600 in PWR steam generator environment has been extensively studied for over 30 years without rendering a clear understanding of the essential mechanisms. The lack of understanding of the IGSCC mechanism is due to a complex interaction of numerous variables such as microstructure, thermomechanical processing, strain rate, water chemistry and electrochemical potential. Hydrogen plays an important role in all these variables. The complexity, however, significantly hinders a clearer and more fundamental understanding of the mechanism of hydrogen in enhancing intergranular cracking via whatever mechanism. In this work, an attemptmore » is made to review the role of hydrogen based on the current understanding of grain boundary structure and chemistry and intergranular fracture of nickel alloys, effect of hydrogen on electrochemical behavior of Alloy 600 and Alloy 690 (e.g. the passive film stability, polarization behavior and open-circuit potential) and effect of hydrogen on PWSCC behavior of Alloy 600 and Alloy 690. Mechanistic studies on the PWSCC are briefly reviewed. It is concluded that further studies on the role of hydrogen on intergranular cracking in both inert and primary side environments are needed. These studies should focus on the correlation of the results obtained at different laboratories by different methods on materials with different metallurgical and chemical parameters.« less

The search for mechanisms of change in behavioral treatments for alcohol use disorders: a commentary.

PubMed

Longabaugh, Richard

2007-10-01

Definitive results from efforts to identify mechanisms of change in behavioral treatments for alcohol use disorders have been elusive. The working hypothesis guiding this paper is that one of the reasons for this elusiveness is that the models we hypothesize to account for treatments effectiveness are unnecessarily restricted and too simple. This paper aims to accomplish 3 things. First, a typography for locating potential mediators of change will be presented. In the course of doing so, a nomenclature will be proposed with the hope that this will facilitate communications among alcohol treatment researchers studying mechanisms of change. Second, alternatives to the classic test of mediation of alcohol treatment effects will be considered and one such alternative described. Third, alternative ways of conceptualizing, constructing and analyzing variables to measure mediators will be suggested. It is hoped that this commentary will facilitate research on mechanisms of change in behavioral treatments for alcohol use disorders. Behavioral change is a complex process, and the models that we develop to account for this process need to reflect this complexity. Advances in statistical approaches for testing mediation, along with a better understanding as to how to use these tools should help in moving toward this goal.

Neurosteroid Influences on Sensitivity to Ethanol

PubMed Central

Helms, Christa M.; Rossi, David J.; Grant, Kathleen A.

2011-01-01

This review will highlight a variety of mechanisms by which neurosteroids affect sensitivity to ethanol, including physiological states associated with activity of the hypothalamic–pituitary–adrenal (HPA) and hypothalamic–pituitary–gonadal (HPG) axes, and the effects of chronic exposure to ethanol, in addition to behavioral implications. To date, γ-aminobutyric acid (GABAA) receptor mechanisms are a major focus of the modulation of ethanol effects by neuroactive steroids. While NMDA receptor mechanisms are gaining prominence in the literature, these complex data would be best discussed separately. Accordingly, GABAA receptor mechanisms are emphasized in this review with brief mention of some NMDA receptor mechanisms to point out contrasting neuroactive steroid pharmacology. Overall, the data suggest that neurosteroids are virtually ubiquitous modulators of inhibitory neurotransmission. Neurosteroids appear to affect sensitivity to ethanol in specific brain regions and, consequently, specific behavioral tests, possibly related to the efficacy and potency of ethanol to potentiate the release of GABA and increase neurosteroid concentrations. Although direct interaction of ethanol and neuroactive steroids at common receptor binding sites has been suggested in some studies, this proposition is still controversial. It is currently difficult to assign a specific mechanism by which neuroactive steroids could modulate the effects of ethanol in particular behavioral tasks. PMID:22654852

Microbial endocrinology: Host-microbiota neuroendocrine interactions influencing brain and behavior.

PubMed

Lyte, Mark

2014-01-01

The ability of microorganisms, whether present as commensals within the microbiota or introduced as part of a therapeutic regimen, to influence behavior has been demonstrated by numerous laboratories over the last few years. Our understanding of the mechanisms that are responsible for microbiota-gut-brain interactions is, however, lacking. The complexity of the microbiota is, of course, a contributing factor. Nonetheless, while microbiologists approaching the issue of microbiota-gut-brain interactions in the behavior well recognize such complexity, what is often overlooked is the equal complexity of the host neurophysiological system, especially within the gut which is differentially innervated by the enteric nervous system. As such, in the search for common mechanisms by which the microbiota may influence behavior one may look for mechanisms which are shared by both host and microbiota. Such interkingdom signaling can be found in the shared production of neurochemical mediators that are found in both eukaryotes and prokaryotes. The study of the production and recognition of neurochemicals that are exactly the same in structure to those produced in the vertebrate organisms is known as microbial endocrinology. The examination of the microbiota from the vantage point of host-microbiota neuroendocrine interactions cannot only identify new microbial endocrinology-based mechanisms by which the microbiota can influence host behavior, but also lead to the design of interventions in which the composition of the microbiota may be modulated in order to achieve a specific microbial endocrinology-based profile beneficial to overall host behavior.

A prototype of behavior selection mechanism based on emotion

NASA Astrophysics Data System (ADS)

Zhang, Guofeng; Li, Zushu

2007-12-01

In bionic methodology rather than in design methodology more familiar with, summarizing the psychological researches of emotion, we propose the biologic mechanism of emotion, emotion selection role in creature evolution and a anima framework including emotion similar to the classical control structure; and consulting Prospect Theory, build an Emotion Characteristic Functions(ECF) that computer emotion; two more emotion theories are added to them that higher emotion is preferred and middle emotion makes brain run more efficiently, emotional behavior mechanism comes into being. A simulation of proposed mechanism are designed and carried out on Alife Swarm software platform. In this simulation, a virtual grassland ecosystem is achieved where there are two kinds of artificial animals: herbivore and preyer. These artificial animals execute four types of behavior: wandering, escaping, finding food, finding sex partner in their lives. According the theories of animal ethnology, escaping from preyer is prior to other behaviors for its existence, finding food is secondly important behavior, rating is third one and wandering is last behavior. In keeping this behavior order, based on our behavior characteristic function theory, the specific functions of emotion computing are built of artificial autonomous animals. The result of simulation confirms the behavior selection mechanism.

Mechanical Behavior of Al-SiC Nanolaminate Composites Using Micro-Scale Testing Methods

NASA Astrophysics Data System (ADS)

Mayer, Carl Randolph

Nanolaminate composite materials consist of alternating layers of materials at the nanoscale (≤100 nm). Due to the nanometer scale thickness of their layers, these materials display unique and tailorable properties. This enables us to alter both mechanical attributes such as strength and wear properties, as well as functional characteristics such as biocompatibility, optical, and electronic properties. This dissertation focuses on understanding the mechanical behavior of the Al-SiC system. From a practical perspective, these materials exhibit a combination of high toughness and strength which is attractive for many applications. Scientifically, these materials are interesting due to the large elastic modulus mismatch between the layers. This, paired with the small layer thickness, allows a unique opportunity for scientists to study the plastic deformation of metals under extreme amounts of constraint. Previous studies are limited in scope and a more diverse range of mechanical characterization is required to understand both the advantages and limitations of these materials. One of the major challenges with testing these materials is that they are only able to be made in thicknesses on the order of micrometers so the testing methods are limited to small volume techniques. This work makes use of both microscale testing techniques from the literature as well as novel methodologies. Using these techniques we are able to gain insight into aspects of the material's mechanical behavior such as the effects of layer orientation, flaw dependent fracture, tension-compression asymmetry, fracture toughness as a function of layer thickness, and shear behavior as a function of layer thickness.

A 3D Culture Model to Study How Fluid Pressure and Flow Affect the Behavior of Aggregates of Epithelial Cells.

PubMed

Piotrowski-Daspit, Alexandra S; Simi, Allison K; Pang, Mei-Fong; Tien, Joe; Nelson, Celeste M

2017-01-01

Cells are surrounded by mechanical stimuli in their microenvironment. It is important to determine how cells respond to the mechanical information that surrounds them in order to understand both development and disease progression, as well as to be able to predict cell behavior in response to physical stimuli. Here we describe a protocol to determine the effects of interstitial fluid flow on the migratory behavior of an aggregate of epithelial cells in a three-dimensional (3D) culture model. This protocol includes detailed methods for the fabrication of a 3D cell culture chamber with hydrostatic pressure control, the culture of epithelial cells as an aggregate in a collagen gel, and the analysis of collective cell behavior in response to pressure-driven flow.

Structural properties and gas sensing behavior of sol-gel grown nanostructured zinc oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajyaguru, Bhargav; Gadani, Keval; Kansara, S. B.

2016-05-06

In this communication, we report the results of the studies on structural properties and gas sensing behavior of nanostructured ZnO grown using acetone precursor based modified sol-gel technique. Final product of ZnO was sintered at different temperatures to vary the crystallite size while their structural properties have been studied using X-ray diffraction (XRD) measurement performed at room temperature. XRD results suggest the single phasic nature of all the samples and crystallite size increases from 11.53 to 20.96 nm with increase in sintering temperature. Gas sensing behavior has been studied for acetone gas which indicates that lower sintered samples are moremore » capable to sense the acetone gas and related mechanism has been discussed in the light of crystallite size, crystal boundary density, defect mechanism and possible chemical reaction between gas traces and various oxygen species.« less

Effects of Ultrasonic Parameters on the Crystallization Behavior of Virgin Coconut Oil.

PubMed

Wu, Linhe; Cao, Jun; Bai, Xinpeng; Chen, Haiming; Zhang, Yuxiang; Wu, Qian

2016-12-01

Crystallization behavior of virgin coconut oil (VCO) in the absence and presence of ultrasonic treatment under a temperature gradient field was investigated. The effects of ultrasonic parameters on the crystallization behavior of VCO were studied by differential scanning calorimetry, ultraviolet/visible spectrophotometry and polarized light microscopy. The thermal effect of the ultrasonic treatment was also increased at higher power levels. Therefore, the optimal power level was determined at approximately 36 W. Induction time reduced evidently and the crystallization rate was accelerated under ultrasonic treatment at crystallization temperature (T c ) above 15°C. However, no significant difference in induction time was noted at 13°C. The result of morphological studies showed that the growth mechanism of crystals was significantly changed. Meanwhile, smaller and uniform crystals were produced by the ultrasonic treatment. This study shows a novel technique to accelerate the crystallization rate and alter the growth mechanism of VCO crystals.

Sorption/Desorption Behavior and Mechanism of NH4(+) by Biochar as a Nitrogen Fertilizer Sustained-Release Material.

PubMed

Cai, Yanxue; Qi, Hejinyan; Liu, Yujia; He, Xiaowei

2016-06-22

Biochar, the pyrolysis product of biomass material with limited oxygen, has the potential to increase crop production and sustained-release fertilizer, but the understanding of the reason for improving soil fertility is insufficient, especially the behavior and mechanism of ammonium sulfate. In this study, the sorption/desorption effect of NH4(+) by biochar deriving from common agricultural wastes under different preparation temperatures from 200 to 500 °C was studied and its mechanism was discussed. The results showed that biochar displayed excellent retention ability in holding NH4(+) above 90% after 21 days under 200 °C preparation temperature, and it can be deduced that the oxygen functional groups, such as carboxyl and keto group, played the primary role in adsorbing NH4(+) due to hydrogen bonding and electrostatic interaction. The sorption/desorption effect and mechanism were studied for providing an optional way to dispose of agricultural residues into biochar as a nitrogen fertilizer sustained-release material under suitable preparation temperature.

Magnetic navigation behavior and the oceanic ecology of young loggerhead sea turtles.

PubMed

Putman, Nathan F; Verley, Philippe; Endres, Courtney S; Lohmann, Kenneth J

2015-04-01

During long-distance migrations, animals navigate using a variety of sensory cues, mechanisms and strategies. Although guidance mechanisms are usually studied under controlled laboratory conditions, such methods seldom allow for navigation behavior to be examined in an environmental context. Similarly, although realistic environmental models are often used to investigate the ecological implications of animal movement, explicit consideration of navigation mechanisms in such models is rare. Here, we used an interdisciplinary approach in which we first conducted lab-based experiments to determine how hatchling loggerhead sea turtles (Caretta caretta) respond to magnetic fields that exist at five widely separated locations along their migratory route, and then studied the consequences of the observed behavior by simulating it within an ocean circulation model. Magnetic fields associated with two geographic regions that pose risks to young turtles (due to cold wintertime temperatures or potential displacement from the migratory route) elicited oriented swimming, whereas fields from three locations where surface currents and temperature pose no such risk did not. Additionally, at locations with fields that elicited oriented swimming, simulations indicate that the observed behavior greatly increases the likelihood of turtles advancing along the migratory pathway. Our findings suggest that the magnetic navigation behavior of sea turtles is intimately tied to their oceanic ecology and is shaped by a complex interplay between ocean circulation and geomagnetic dynamics. © 2015. Published by The Company of Biologists Ltd.

Effect of suction hysteresis on resilient modulus of fine-grained cohesionless soil.

DOT National Transportation Integrated Search

2010-07-30

The mechanical behavior of subgrade soil is influenced by the seasonal variations in moisture content. To better understand this behavior, it is crucial to study the relationship between soil moisture content and matric suction known as the Soil Wate...

Zonal Articular Cartilage Possesses Complex Mechanical Behavior Spanning Multiple Length Scales: Dependence on Chemical Heterogeneity, Anisotropy, and Microstructure

NASA Astrophysics Data System (ADS)

Wahlquist, Joseph A.

This work focused on characterizing the mechanical behavior of biological material in physiologically relevant conditions and at sub millimeter length scales. Elucidating the time, length scale, and directionally dependent mechanical behavior of cartilage and other biological materials is critical to adequately recapitulate native mechanosensory cues for cells, create computational models that mimic native tissue behavior, and assess disease progression. This work focused on three broad aspects of characterizing the mechanical behavior of articular cartilage. First, we sought to reveal the causes of time-dependent deformation and variation of mechanical properties with distance from the articular surface. Second, we investigated size dependence of mechanical properties. Finally, we examined material anisotropy of both the calcified and uncalcified tissues of the osteochondral interface. This research provides insight into how articular cartilage serves to support physiologic loads and simultaneously sustain chondrocyte viability.

What Works for Whom, How and under What Circumstances? Testing Moderated Mediation of Intervention Effects on Externalizing Behavior in Children

ERIC Educational Resources Information Center

Stoltz, Sabine; Dekovic, Maja; van Londen, Monique; de Castro, Bram Orobio; Prinzie, Peter

2013-01-01

In this study, we investigate whether changes in child social cognitive functioning and parenting are the mechanisms through which an individually delivered real-world child intervention, Stay Cool Kids, aimed at preventing externalizing problem behavior in high-risk elementary school children, induces changes in child behavior. Moreover, we…

Recent advances in applied research on DRO procedures.

PubMed

Jessel, Joshua; Ingvarsson, Einar T

2016-12-01

Differential reinforcement of other behavior (DRO) has been applied to reduce problem behavior in various forms across different populations. We review DRO research from the last 5 years, with a focus on studies that enhance our understanding of the underlying mechanisms of DRO. We also discuss implications for practitioners and applied researchers. © 2016 Society for the Experimental Analysis of Behavior.

Perinatal Factors, Parenting Behavior, and Reactive Aggression: Does Cortisol Reactivity Mediate This Developmental Risk Process?

ERIC Educational Resources Information Center

Ryan, Stacy R.; Schechter, Julia C.; Brennan, Patricia A.

2012-01-01

Little is known about the mechanisms of action that link perinatal risk and the development of aggressive behavior. The aim of this study was to examine whether perinatal risk and parenting interacted to specifically predict reactive aggression, as opposed to general aggressive behavior, and to examine cortisol reactivity as a mediator of this…

Is an epigenetic switch the key to persistent extinction?

PubMed Central

Stafford, James M.; Lattal, K. Matthew

2011-01-01

Many studies of learning have demonstrated that conditioned behavior can be eliminated when previously established relations between stimuli are severed. This extinction process has been extremely important for the development of learning theories and, more recently, for delineating the neurobiological mechanisms that underlie memory. A key finding from behavioral studies of extinction is that extinction eliminates behavior without eliminating the original memory; extinguished behavior often returns with time or with a return to the context in which the original learning occurred. This persistence of the original memory after extinction creates a challenge for clinical applications that use extinction as part of a treatment intervention. Consequently, a goal of recent neurobiological research on extinction is to identify potential pharmacological targets that may result in persistent extinction. Drugs that promote epigenetic changes are particularly promising because they can result in a long-term molecular signal that, combined with the appropriate behavioral treatment, can cause persistent changes in behavior induced by extinction. We will review evidence demonstrating extinction enhancements by drugs that target epigenetic mechanisms and will describe some of the challenges that epigenetic approaches face in promoting persistent suppression of memories. PMID:21536141

Differences in Acute Alcohol-Induced Behavioral Responses Among Zebrafish Populations

PubMed Central

Gerlai, Robert; Ahmad, Fahad; Prajapati, Sonal

2009-01-01

Background With the arsenal of genetic tools available for zebrafish, this species has been successfully used to investigate the genetic aspects of human diseases from developmental disorders to cancer. Interest in the behavior and brain function of zebrafish is also increasing as CNS disorders may be modeled and studied with this species. Alcoholism and alcohol abuse are among the most devastating and costliest diseases. However, the mechanisms of these diseases are not fully understood. Zebrafish has been proposed as a model organism to study such mechanisms. Characterization of alcohol’s effects on zebrafish is a necessary step in this research. Methods Here, we compare the effects of acute alcohol (EtOH) administration on the behavior of zebrafish from 4 distinct laboratory-bred populations using automated as well as observation based behavioral quantification methods. Results Alcohol treatment resulted in significant dose-dependent behavioral changes but the dose–response trajectories differed among zebrafish populations. Conclusions The results demonstrate for the first time a genetic component in alcohol responses in adult zebrafish and also show the feasibility of high throughput behavioral screening. We discuss the exploration and exploitation of the genetic differences found. PMID:18652595

Assessing the relationship between quality of life and behavioral activation using the Japanese Behavioral Activation for Depression Scale-Short Form.

PubMed

Shudo, Yusuke; Yamamoto, Tatsuya

2017-01-01

Quality of life (QOL) is an important health-related concept. Identifying factors that affect QOL can help develop and improve health-promotion interventions. Previous studies suggest that behavioral activation fosters subjective QOL, including well-being. However, the mechanism by which behavioral activation improves QOL is not clear. Considering that QOL improves when depressive symptoms improve post-treatment and that behavioral activation is an effective treatment for depression, it is possible that behavioral activation affects QOL indirectly rather than directly. To clarify the mechanism of the influence of behavioral activation on QOL, it is necessary to examine the relationships between factors related to behavioral activation, depressive symptoms, and QOL. Therefore, we attempted to examine the relationship between these factors. Participants comprised 221 Japanese undergraduate students who completed questionnaires on behavioral activation, QOL, and depressive symptoms: the Japanese versions of the Behavioral Activation for Depression Scale-Short Form (BADS-SF), WHO Quality of Life-BREF (WHOQOL-26), and Center for Epidemiologic Studies Depression Scale (CES-D). The BADS-SF comprises two subscales, Activation and Avoidance, and the WHOQOL-26 measures overall QOL and four domains, Physical Health, Psychological Health, Social Relationships, and Environment. Mediation analyses were conducted with BADS-SF activation and avoidance as independent variables, CES-D as a mediator variable, and each WHO-QOL as an outcome variable. Results indicated that depression completely mediated the relationship between Avoidance and QOL, and partially mediated the relationship between Activation and QOL. In addition, analyses of each domain of QOL showed that Activation positively affected all aspects of QOL directly and indirectly, but Avoidance had a negative influence on only part of QOL mainly through depression. The present study provides behavioral activation strategies aimed at QOL enhancement.

Evaluation of Possible Proximate Mechanisms Underlying the Kinship Theory of Intragenomic Conflict in Social Insects.

PubMed

Galbraith, David A; Yi, Soojin V; Grozinger, Christina M

2016-12-01

Kinship theory provides a universal framework in which to understand the evolution of altruism, but there are many molecular and genetic mechanisms that can generate altruistic behaviors. Interestingly, kinship theory specifically predicts intragenomic conflict between maternally-derived alleles (matrigenes) and paternally-derived alleles (patrigenes) over the generation of altruistic behavior in cases where the interests of the matrigenes and patrigenes are not aligned. Under these conditions, individual differences in selfish versus altruistic behavior are predicted to arise from differential expression of the matrigenes and patrigenes (parent-specific gene expression or PSGE) that regulate selfish versus altruistic behaviors. As one of the leading theories to describe PSGE and genomic imprinting, kinship theory has been used to generate predictions to describe the reproductive division of labor in social insect colonies, which represents an excellent model system to test the hypotheses of kinship theory and examine the underlying mechanisms driving it. Recent studies have confirmed the predicted differences in the influence of matrigenes and patrigenes on reproductive division of labor in social insects, and demonstrated that these differences are associated with differences in PSGE of key genes involved in regulating reproductive physiology, providing further support for kinship theory. However, the mechanisms mediating PSGE in social insects, and how PSGE leads to differences in selfish versus altruistic behavior, remain to be determined. Here, we review the available supporting evidence for three possible epigenetic mechanisms (DNA methylation, piRNAs, and histone modification) that may generate PSGE in social insects, and discuss how these may lead to variation in social behavior. © The Author 2016. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.

Thermal-Mechanical Response of Cracked Satin Weave CFRP Composites at Cryogenic Temperatures

NASA Astrophysics Data System (ADS)

Watanabe, S.; Shindo, Y.; Narita, F.; Takeda, T.

2008-03-01

This paper examines the thermal-mechanical response of satin weave carbon fiber reinforced polymer (CFRP) laminates with internal and/or edge cracks subjected to uniaxial tension load at cryogenic temperatures. Cracks are considered to occur in the transverse fiber bundles and extend through the entire thickness of the fiber bundles. Two-dimentional generalized plane strain finite element models are developed to study the effects of residual thermal stresses and cracks on the mechanical behavior of CFRP woven laminates. A detailed examination of the Young's modulus and stress distributions near the crack tip is carried out which provides insight into material behavior at cryogenic temperatures.

A contextual model of self-regulation change mechanisms among individuals with addictive disorders.

PubMed

Roos, Corey R; Witkiewitz, Katie

2017-11-01

Numerous behavioral treatments for addictive disorders include components explicitly aimed at targeting self-regulation (e.g., coping and emotion regulation). We first provide a summary of key findings to date among studies that have examined self-regulation as a mechanism of behavior change (MOBC) in behavioral treatments for addictive disorders. Based on our review, we conclude that the role of self-regulation as a MOBC across behavioral treatments for addictive disorders is not well-characterized and findings are inconsistent across studies. For example, our review indicates that there is still inconsistent evidence that coping is a unique MOBC in cognitive-behavioral approaches for addictive behaviors. We propose that there has been slow progress in understanding self-regulation as a MOBC in addiction treatment because of a lack of attention to contextual factors. Accordingly, in the second half of this paper, we propose a contextual model of self-regulation change mechanisms, which emphasizes that the role of various facets of self-regulation as MOBC may depend on contextual factors in the immediate situational context (e.g., fluctuating internal and external cues) and in the broader context in which an individual is embedded (e.g., major life stressors, environmental conditions, dispositions). Additionally, we provide specific recommendations to guide future research for understanding both between-person and within-person self-regulation MOBC in addiction treatment. In particular, we provide key recommendations for how to capitalize on intensive longitudinal measurement methods (e.g., ecological momentary assessment) when bringing a contextual perspective to the study of self-regulation as MOBC in various addiction treatments. Copyright © 2017 Elsevier Ltd. All rights reserved.

Assessing the efficacy of imagery-enhanced cognitive behavioral group therapy for social anxiety disorder: Study protocol for a randomized controlled trial.

PubMed

McEvoy, Peter M; Moulds, Michelle L; Grisham, Jessica R; Holmes, Emily A; Moscovitch, David A; Hendrie, Delia; Saulsman, Lisa M; Lipp, Ottmar V; Kane, Robert T; Rapee, Ronald M; Hyett, Matthew P; Erceg-Hurn, David M

2017-09-01

Cognitive behavior group therapy (CBGT) is effective for social anxiety disorder (SAD), but a substantial proportion of patients do not typically achieve normative functioning. Cognitive behavioral models of SAD emphasize negative self-imagery as an important maintaining factor, and evidence suggests that imagery is a powerful cognitive mode for facilitating affective change. This study will compare two group CBGT interventions, one that predominantly uses verbally-based strategies (VB-CBGT) and another that predominantly uses imagery-enhanced strategies (IE-CBGT), in terms of (a) efficacy, (b) mechanisms of change, and (c) cost-effectiveness. This study is a parallel groups (two-arm) single-blind randomized controlled trial. A minimum of 96 patients with SAD will be recruited within a public outpatient community mental health clinic in Perth, Australia. The primary outcomes will be self-reported symptom severity, caseness (SAD present: yes/no) based on a structured diagnostic interview, and clinician-rated severity and life impact. Secondary outcomes and mechanism measures include blind observer-rated use of safety behaviors, physiological activity (heart rate variability and skin conductance level) during a standardized speech task, negative self-beliefs, imagery suppression, fear of negative and positive evaluation, repetitive negative thinking, anxiety, depression, self-consciousness, use of safety behaviors, and the EQ-5D-5L and TiC-P for the health economic analysis. Homework completion, group cohesion, and working alliance will also be monitored. The outcomes of this trial will inform clinicians as to whether integrating imagery-based strategies in cognitive behavior therapy for SAD is likely to improve outcomes. Common and distinct mechanisms of change might be identified, along with relative cost-effectiveness of each intervention. Copyright © 2017 Elsevier Inc. All rights reserved.

Peptidoglycan sensing by octopaminergic neurons modulates Drosophila oviposition

PubMed Central

Kurz, C Leopold; Charroux, Bernard; Chaduli, Delphine; Viallat-Lieutaud, Annelise; Royet, Julien

2017-01-01

As infectious diseases pose a threat to host integrity, eukaryotes have evolved mechanisms to eliminate pathogens. In addition to develop strategies reducing infection, animals can engage in behaviors that lower the impact of the infection. The molecular mechanisms by which microbes impact host behavior are not well understood. We demonstrate that bacterial infection of Drosophila females reduces oviposition and that peptidoglycan, the component that activates Drosophila antibacterial response, is also the elicitor of this behavioral change. We show that peptidoglycan regulates egg-laying rate by activating NF-κB signaling pathway in octopaminergic neurons and that, a dedicated peptidoglycan degrading enzyme acts in these neurons to buffer this behavioral response. This study shows that a unique ligand and signaling cascade are used in immune cells to mount an immune response and in neurons to control fly behavior following infection. This may represent a case of behavioral immunity. DOI: http://dx.doi.org/10.7554/eLife.21937.001 PMID:28264763

Effects of Neutral Toys on Sex-Typed Play in Children with Gender Identity Disorder.

ERIC Educational Resources Information Center

Doering, Robert W.; And Others

The study of typical gender development suggests that both approach and avoidance mechanisms are involved in the eventual display of sex-typed behavior. Some experiments have attempted to demonstrate the independent contribution of these two parameters. Studies suggest that avoidance behavior for cross-sex toys is a useful index of sex-role…

Attention Problems Mediate the Association between Severity of Physical Abuse and Aggressive Behavior in a Sample of Maltreated Early Adolescents

ERIC Educational Resources Information Center

Garrido, Edward F.; Taussig, Heather N.; Culhane, Sara E.; Raviv, Tali

2011-01-01

Empirical evidence has accumulated documenting an association between childhood physical abuse and aggressive behavior. Relatively fewer studies have explored possible mediating mechanisms that may explain this association. The purpose of the current study was to examine whether caregiver- and youth-reported attention problems mediate the…

Gambling and the Reasoned Action Model: Predicting Past Behavior, Intentions, and Future Behavior.

PubMed

Dahl, Ethan; Tagler, Michael J; Hohman, Zachary P

2018-03-01

Gambling is a serious concern for society because it is highly addictive and is associated with a myriad of negative outcomes. The current study applied the Reasoned Action Model (RAM) to understand and predict gambling intentions and behavior. Although prior studies have taken a reasoned action approach to understand gambling, no prior study has fully applied the RAM or used the RAM to predict future gambling. Across two studies the RAM was used to predict intentions to gamble, past gambling behavior, and future gambling behavior. In study 1 the model significantly predicted intentions and past behavior in both a college student and Amazon Mechanical Turk sample. In study 2 the model predicted future gambling behavior, measured 2 weeks after initial measurement of the RAM constructs. This study stands as the first to show the utility of the RAM in predicting future gambling behavior. Across both studies, attitudes and perceived normative pressure were the strongest predictors of intentions to gamble. These findings provide increased understanding of gambling and inform the development of gambling interventions based on the RAM.

Using an Adoption–Biological Family Design to Examine Associations Between Maternal Trauma, Maternal Depressive Symptoms, and Child Internalizing and Externalizing Behaviors

PubMed Central

Grabow, Aleksandria Perez; Khurana, Atika; Natsuaki, Misaki N.; Neiderhiser, Jenae M.; Harold, Gordon T.; Shaw, Daniel S.; Ganiban, Jody M.; Reiss, David; Leve, Leslie D.

2017-01-01

Maternal trauma is a complex risk factor that has been linked to adverse child outcomes, yet the mechanisms underlying this association are not well understood. This study, which included adoptive and biological families, examined the heritable and environmental mechanisms by which maternal trauma and associated depressive symptoms are linked to child internalizing and externalizing behaviors. Path analyses were used to analyze data from 541 adoptive mother–adopted child (AM–AC) dyads and 126 biological mother–biological child (BM–BC) dyads; the two family types were linked through the same biological mother. Rearing mother’s trauma was associated with child internalizing and externalizing behaviors in AM–AC and BM–BC dyads, and this association was mediated by rearing mothers’ depressive symptoms, with the exception of biological child externalizing behavior, for which biological mother trauma had a direct influence only. Significant associations between maternal trauma and child behavior in dyads that share only environment (i.e., AM–AC dyads) suggest an environmental mechanism of influence for maternal trauma. Significant associations were also observed between maternal depressive symptoms and child internalizing and externalizing behavior in dyads that were only genetically related, with no shared environment (i.e., BM–AC dyads), suggesting a heritable pathway of influence via maternal depressive symptoms. PMID:29162177

Using an adoption-biological family design to examine associations between maternal trauma, maternal depressive symptoms, and child internalizing and externalizing behaviors.

PubMed

Grabow, Aleksandria Perez; Khurana, Atika; Natsuaki, Misaki N; Neiderhiser, Jenae M; Harold, Gordon T; Shaw, Daniel S; Ganiban, Jody M; Reiss, David; Leve, Leslie D

2017-12-01

Maternal trauma is a complex risk factor that has been linked to adverse child outcomes, yet the mechanisms underlying this association are not well understood. This study, which included adoptive and biological families, examined the heritable and environmental mechanisms by which maternal trauma and associated depressive symptoms are linked to child internalizing and externalizing behaviors. Path analyses were used to analyze data from 541 adoptive mother-adopted child (AM-AC) dyads and 126 biological mother-biological child (BM-BC) dyads; the two family types were linked through the same biological mother. Rearing mother's trauma was associated with child internalizing and externalizing behaviors in AM-AC and BM-BC dyads, and this association was mediated by rearing mothers' depressive symptoms, with the exception of biological child externalizing behavior, for which biological mother trauma had a direct influence only. Significant associations between maternal trauma and child behavior in dyads that share only environment (i.e., AM-AC dyads) suggest an environmental mechanism of influence for maternal trauma. Significant associations were also observed between maternal depressive symptoms and child internalizing and externalizing behavior in dyads that were only genetically related, with no shared environment (i.e., BM-AC dyads), suggesting a heritable pathway of influence via maternal depressive symptoms.

Invertebrate models of alcoholism.

PubMed

Scholz, Henrike; Mustard, Julie A

2013-01-01

For invertebrates to become useful models for understanding the genetic and physiological mechanisms of alcoholism related behaviors and the predisposition towards alcoholism, several general requirements must be fulfilled. The animal should encounter ethanol in its natural habitat, so that the central nervous system of the organism will have evolved mechanisms for responding to ethanol exposure. How the brain adapts to ethanol exposure depends on its access to ethanol, which can be regulated metabolically and/or by physical barriers. Therefore, a model organism should have metabolic enzymes for ethanol degradation similar to those found in humans. The neurons and supporting glial cells of the model organism that regulate behaviors affected by ethanol should share the molecular and physiological pathways found in humans, so that results can be compared. Finally, the use of invertebrate models should offer advantages over traditional model systems and should offer new insights into alcoholism-related behaviors. In this review we will summarize behavioral similarities and identified genes and mechanisms underlying ethanol-induced behaviors in invertebrates. This review mainly focuses on the use of the nematode Caenorhabditis elegans, the honey bee Apis mellifera and the fruit fly Drosophila melanogaster as model systems. We will discuss insights gained from those studies in conjunction with their vertebrate model counterparts and the implications for future research into alcoholism and alcohol-induced behaviors.

Carbon nanotubes reinforced chitosan films: mechanical properties and cell response of a novel biomaterial for cardiovascular tissue engineering.

PubMed

Kroustalli, A; Zisimopoulou, A E; Koch, S; Rongen, L; Deligianni, D; Diamantouros, S; Athanassiou, G; Kokozidou, M; Mavrilas, D; Jockenhoevel, S

2013-12-01

Carbon nanotubes have been proposed as fillers to reinforce polymeric biomaterials for the strengthening of their structural integrity to achieve better biomechanical properties. In this study, a new polymeric composite material was introduced by incorporating various low concentrations of multiwalled carbon nanotubes (MWCNTs) into chitosan (CS), aiming at achieving a novel composite biomaterial with superior mechanical and biological properties compared to neat CS, in order to be used in cardiovascular tissue engineering applications. Both mechanical and biological characteristics in contact with the two relevant cell types (endothelial cells and vascular myofibroblasts) were studied. Regarding the mechanical behavior of MWCNT reinforced CS (MWCNT/CS), 5 and 10 % concentrations of MWCNTs enhanced the mechanical behavior of CS, with that of 5 % exhibiting a superior mechanical strength compared to 10 % concentration and neat CS. Regarding biological properties, MWCNT/CS best supported proliferation of endothelial and myofibroblast cells, MWCNTs and MWCNT/CS caused no apoptosis and were not toxic of the examined cell types. Conclusively, the new material could be suitable for tissue engineering (TE) and particularly for cardiovascular TE applications.

Recent Translational Findings on Impulsivity in Relation to Drug Abuse

PubMed Central

Weafer, Jessica; Mitchell, Suzanne H.

2015-01-01

Impulsive behavior is strongly implicated in drug abuse, as both a cause and a consequence of drug use. To understand how impulsive behaviors lead to and result from drug use, translational evidence from both human and non-human animal studies is needed. Here, we review recent (2009 or later) studies that have investigated two major components of impulsive behavior, inhibitory control and impulsive choice, across preclinical and clinical studies. We concentrate on the stop-signal task as the measure of inhibitory control and delay discounting as the measure of impulsive choice. Consistent with previous reports, recent studies show greater impulsive behavior in drug users compared with non-users. Additionally, new evidence supports the prospective role of impulsive behavior in drug abuse, and has begun to identify the neurobiological mechanisms underlying impulsive behavior. We focus on the commonalities and differences in findings between preclinical and clinical studies, and suggest future directions for translational research. PMID:25678985

Skin mechanical properties and modeling: A review.

PubMed

Joodaki, Hamed; Panzer, Matthew B

2018-04-01

The mechanical properties of the skin are important for various applications. Numerous tests have been conducted to characterize the mechanical behavior of this tissue, and this article presents a review on different experimental methods used. A discussion on the general mechanical behavior of the skin, including nonlinearity, viscoelasticity, anisotropy, loading history dependency, failure properties, and aging effects, is presented. Finally, commonly used constitutive models for simulating the mechanical response of skin are discussed in the context of representing the empirically observed behavior.

Analytical study of index-coupled herd behavior in financial markets

NASA Astrophysics Data System (ADS)

Berman, Yonatan; Shapira, Yoash; Schwartz, Moshe

2016-12-01

Herd behavior in financial markets had been investigated extensively in the past few decades. Scholars have argued that the behavioral tendency of traders and investors to follow the market trend, notably reflected in indices both on short and long time scales, is substantially affecting the overall market behavior. Research has also been devoted to revealing these behaviors and characterizing the market herd behavior. In this paper we present a simple herd behavior model for the dynamics of financial variables by introducing a simple coupling mechanism of stock returns to the index return, deriving analytic expressions for statistical properties of the returns. We found that several important phenomena in the stock market, namely the correlations between stock market returns and the exponential decay of short-term autocorrelations, are derived from our model. These phenomena have been given various explanations and theories, with herd market behavior being one of the leading. We conclude that the coupling mechanism, which essentially encapsulates the herd behavior, indeed creates correlation and autocorrelation. We also show that this introduces a time scale to the system, which is the characteristic time lag between a change in the index and its effect on the return of a stock.

Analysis of the Negative-SET Behaviors in Cu/ZrO2/Pt Devices

NASA Astrophysics Data System (ADS)

Liu, Sen; Zhao, Xiaolong; Li, Qingjiang; Li, Nan; Wang, Wei; Liu, Qi; Xu, Hui

2016-12-01

Metal oxide-based electrochemical metallization memory (ECM) shows promising performance for next generation non-volatile memory. The negative-SET behavior has been observed in various oxide-based ECM devices. But the underlying mechanism of this behavior remains unaddressed and the role of the metal cation and oxygen vacancy in this behavior is unclear. In this work, we have observed two kinds of negative-SET (labeled as N-SET1 and N-SET2) behaviors in our Cu/ZrO2/Pt devices. Both the two behaviors can result in hard breakdown due to the high compliance current in reset process. The I-V characteristic shows that the two negative-SET behaviors have an obvious difference in operation voltage. Using four-probe resistance measurement method, the resistance-temperature characteristics of the ON-state after various negative-SET behaviors have been studied. The temperature dependence results demonstrate that the N-SET1 behavior is dominated by Cu conductive filament (CF) reformation caused by the Cu CF overgrowth phenomenon while the N-SET2 is related to the formation of oxygen vacancy CF. This work may provide a comprehensive understanding of the switching mechanism in oxide-based ECM devices.

The genetic and environmental foundations of political, psychological, social, and economic behaviors: a panel study of twins and families.

PubMed

Hatemi, Peter K; Smith, Kevin; Alford, John R; Martin, Nicholas G; Hibbing, John R

2015-06-01

Here we introduce the Genetic and Environmental Foundations of Political and Economic Behaviors: A Panel Study of Twins and Families (PIs Alford, Hatemi, Hibbing, Martin, and Smith). This study was designed to explore the genetic and environmental influences on social, economic, and political behaviors and attitudes. It involves identifying the psychological mechanisms that operate on these traits, the heritability of complex economic and political traits under varying conditions, and specific genetic correlates of attitudes and behaviors. In addition to describing the study, we conduct novel analyses on the data, estimating the heritability of two traits so far unexplored in the extant literature: Machiavellianism and Baron-Cohen's Empathizing Quotient.

Development of social skills in children: neural and behavioral evidence for the elaboration of cognitive models

PubMed Central

Soto-Icaza, Patricia; Aboitiz, Francisco; Billeke, Pablo

2015-01-01

Social skills refer to a wide group of abilities that allow us to interact and communicate with others. Children learn how to solve social situations by predicting and understanding other's behaviors. The way in which humans learn to interact successfully with others encompasses a complex interaction between neural, behavioral, and environmental elements. These have a role in the accomplishment of positive developmental outcomes, including peer acceptance, academic achievement, and mental health. All these social abilities depend on widespread brain networks that are recently being studied by neuroscience. In this paper, we will first review the studies on this topic, aiming to clarify the behavioral and neural mechanisms related to the acquisition of social skills during infancy and their appearance in time. Second, we will briefly describe how developmental diseases like Autism Spectrum Disorders (ASD) can inform about the neurobiological mechanisms of social skills. We finally sketch a general framework for the elaboration of cognitive models in order to facilitate the comprehension of human social development. PMID:26483621

The evolution of Drosophila melanogaster as a model for alcohol research.

PubMed

Devineni, Anita V; Heberlein, Ulrike

2013-07-08

Animal models have been widely used to gain insight into the mechanisms underlying the acute and long-term effects of alcohol exposure. The fruit fly Drosophila melanogaster encounters ethanol in its natural habitat and possesses many adaptations that allow it to survive and thrive in ethanol-rich environments. Several assays to study ethanol-related behaviors in flies, ranging from acute intoxication to self-administration and reward, have been developed in the past 20 years. These assays have provided the basis for studying the physiological and behavioral effects of ethanol and for identifying genes mediating these effects. In this review we describe the ecological relationship between flies and ethanol, the effects of ethanol on fly development and behavior, the use of flies as a model for alcohol addiction, and the interaction between ethanol and social behavior. We discuss these advances in the context of their utility to help decipher the mechanisms underlying the diverse effects of ethanol, including those that mediate ethanol dependence and addiction in humans.

Development of social skills in children: neural and behavioral evidence for the elaboration of cognitive models.

PubMed

Soto-Icaza, Patricia; Aboitiz, Francisco; Billeke, Pablo

2015-01-01

Social skills refer to a wide group of abilities that allow us to interact and communicate with others. Children learn how to solve social situations by predicting and understanding other's behaviors. The way in which humans learn to interact successfully with others encompasses a complex interaction between neural, behavioral, and environmental elements. These have a role in the accomplishment of positive developmental outcomes, including peer acceptance, academic achievement, and mental health. All these social abilities depend on widespread brain networks that are recently being studied by neuroscience. In this paper, we will first review the studies on this topic, aiming to clarify the behavioral and neural mechanisms related to the acquisition of social skills during infancy and their appearance in time. Second, we will briefly describe how developmental diseases like Autism Spectrum Disorders (ASD) can inform about the neurobiological mechanisms of social skills. We finally sketch a general framework for the elaboration of cognitive models in order to facilitate the comprehension of human social development.

Elucidating the mechanisms linking early pubertal timing, sexual activity, and substance use for maltreated versus nonmaltreated adolescents.

PubMed

Negriff, Sonya; Brensilver, Matthew; Trickett, Penelope K

2015-06-01

To test models linking pubertal timing, peer substance use, sexual behavior, and substance use for maltreated versus comparison adolescents. Three theoretical mechanisms were tested: (1) peer influence links early pubertal timing to later sexual behavior and substance use; (2) early maturers engage in substance use on their own and then select substance-using friends; or (3) early maturers initiate sexual behaviors which lead them to substance-using peers. The data came from a longitudinal study of the effects of child maltreatment on adolescent development (303 maltreated and 151 comparison adolescents; age, 9-13 years at initial wave). Multiple-group structural equation models tested the hypotheses across three time points including variables of pubertal timing, perception of peer substance use, sexual behavior, and self-reported substance use. Early pubertal timing was associated with substance-using peers only for maltreated adolescents, indicating the mediation path from early pubertal timing through substance-using peers to subsequent adolescent substance use and sexual behavior only holds for maltreated adolescents. Mediation via sexual behavior was significant for both maltreated and comparison adolescents. This indicates that sexual behavior may be a more universal mechanism linking early maturation with risky friends regardless of adverse life experiences. The findings are a step toward elucidating the developmental pathways from early puberty to risk behavior and identifying early experiences that may alter mediation effects. Copyright © 2015 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

Is Alcoholics Anonymous religious, spiritual, neither? Findings from 25 years of mechanisms of behavior change research.

PubMed

Kelly, John F

2017-06-01

Alcoholics Anonymous (AA) is a world-wide recovery mutual-help organization that continues to arouse controversy. In large part, concerns persist because of AA's ostensibly quasi-religious/spiritual orientation and emphasis. In 1990 the United States' Institute of Medicine called for more studies on AA's effectiveness and its mechanisms of behavior change (MOBC) stimulating a flurry of federally funded research. This paper reviews the religious/spiritual origins of AA and its program and contrasts its theory with findings from this latest research. Literature review, summary and synthesis of studies examining AA's MOBC. While AA's original main text ('the Big Book', 1939) purports that recovery is achieved through quasi-religious/spiritual means ('spiritual awakening'), findings from studies on MOBC suggest this may be true only for a minority of participants with high addiction severity. AA's beneficial effects seem to be carried predominantly by social, cognitive and affective mechanisms. These mechanisms are more aligned with the experiences reported by AA's own larger and more diverse membership as detailed in its later social, cognitive and behaviorally oriented publications (e.g. Living Sober, 1975) written when AA membership numbered more than a million men and women. Alcoholics Anonymous appears to be an effective clinical and public health ally that aids addiction recovery through its ability to mobilize therapeutic mechanisms similar to those mobilized in formal treatment, but is able to do this for free over the long term in the communities in which people live. © 2016 Society for the Study of Addiction.

Portion Size: Latest Developments and Interventions.

PubMed

Steenhuis, Ingrid; Poelman, Maartje

2017-03-01

The aim of this review is to provide an overview of (1) underlying mechanisms of the effect of portion size on energy intake, (2) external factors explaining the portion size effect and (3) interventions and measurements aimed at food portion size. Previous studies have shown that portion sizes have increased in recent decades. Many experimental studies have been conducted to unravel the mechanisms underlying the portion-size effect on food intake (e.g. the appropriateness mechanism, the 'unit bias' mechanism, the 'previous experience/expectation' mechanism, the 'visual cue' mechanism and the 'bite size' mechanism). In addition, external factors have been found to drive food portion selection and consumption (e.g. value for money, mindless eating, levels of awareness, estimation bias. Research on several interventions (ranging from 'providing information' to 'eliminating choice') have been conducted, but remain scarce, especially intervention studies in which portion size is a key focus in weight loss. Moreover, only three new instruments with respect to portion control behavior have been developed. There is considerable evidence for the portion-size effect on energy intake. However, the work on interventions targeting portion size and measurements for portion control behavior are limited. Moreover, from the literature it is not yet clear what type of interventions work best, for whom and in what context.

Differences in time-dependent mechanical properties between extruded and molded hydrogels

PubMed Central

Ersumo, N; Witherel, CE; Spiller, KL

2016-01-01

The mechanical properties of hydrogels used in biomaterials and tissue engineering applications are critical determinants of their functionality. Despite the recent rise of additive manufacturing, and specifically extrusion-based bioprinting, as a prominent biofabrication method, comprehensive studies investigating the mechanical behavior of extruded constructs remain lacking. To address this gap in knowledge, we compared the mechanical properties and swelling properties of crosslinked gelatin-based hydrogels prepared by conventional molding techniques or by 3D bioprinting using a BioBots Beta pneumatic extruder. A preliminary characterization of the impact of bioprinting parameters on construct properties revealed that both Young's modulus and optimal extruding pressure increased with polymer content, and that printing resolution increased with both printing speed and nozzle gauge. High viability (>95%) of encapsulated NIH 3T3 fibroblasts confirmed the cytocompatibility of the construct preparation process. Interestingly, the Young's moduli of extruded and molded constructs were not different, but extruded constructs did show increases in both the rate and extent of time-dependent mechanical behavior observed in creep. Despite similar polymer densities, extruded hydrogels showed greater swelling over time compared to molded hydrogels, suggesting that differences in creep behavior derived from differences in microstructure and fluid flow. Because of the crucial roles of time-dependent mechanical properties, fluid flow, and swelling properties on tissue and cell behavior, these findings highlight the need for greater consideration of the effects of the extrusion process on hydrogel properties. PMID:27550945

A Novel Approach to Primary Cell Culture for Octopus vulgaris Neurons

PubMed Central

Maselli, Valeria; Xu, Fenglian; Syed, Naweed I.; Polese, Gianluca; Di Cosmo, Anna

2018-01-01

Octopus vulgaris is a unique model system for studying complex behaviors in animals. It has a large and centralized nervous system made up of lobes that are involved in controlling various sophisticated behaviors. As such, it may be considered as a model organism for untangling the neuronal mechanisms underlying behaviors—including learning and memory. However, despite considerable efforts, Octopus lags behind its other counterparts vis-à-vis its utility in deciphering the cellular, molecular and synaptic mechanisms underlying various behaviors. This study represents a novel approach designed to establish a neuronal cell culture protocol that makes this species amenable to further exploitation as a model system. Here we developed a protocol that enables dissociation of neurons from two specific Octopus' brain regions, the vertical-superior frontal system and the optic lobes, which are involved in memory, learning, sensory integration and adult neurogenesis. In particular, cells dissociated with enzyme papain and cultured on Poly-D-Lysine-coated dishes with L15-medium and fetal bovine serum yielded high neuronal survival, axon growth, and re-growth after injury. This model was also explored to define optimal culture conditions and to demonstrate the regenerative capabilities of adult Octopus neurons after axotomy. This study thus further underscores the importance of Octopus neurons as a model system for deciphering fundamental molecular and cellular mechanism of complex brain function and underlying behaviors. PMID:29666582

Load Diffusion in Composite Structures

NASA Technical Reports Server (NTRS)

Horgan, Cornelius O.; Simmonds, J. G.

2000-01-01

This research has been concerned with load diffusion in composite structures. Fundamental solid mechanics studies were carried out to provide a basis for assessing the complicated modeling necessary for large scale structures used by NASA. An understanding of the fundamental mechanisms of load diffusion in composite subcomponents is essential in developing primary composite structures. Analytical models of load diffusion behavior are extremely valuable in building an intuitive base for developing refined modeling strategies and assessing results from finite element analyses. The decay behavior of stresses and other field quantities provides a significant aid towards this process. The results are also amendable to parameter study with a large parameter space and should be useful in structural tailoring studies.

Sexual Experience in Female Rodents: Cellular Mechanisms and Functional Consequences

PubMed Central

Meisel, Robert L.; Mullins, Amanda J.

2007-01-01

The neurobiology of female sexual behavior has largely focused on mechanisms of hormone action on nerve cells and how these effects translate into the display of copulatory motor patterns. Of equal importance, though less studied, are some of the consequences of engaging in sexual behavior, including the rewarding properties of sexual interactions and how sexual experience alters copulatory efficiency. This review summarizes the effects of sexual experience on reward processes and copulation in female Syrian hamsters. Neural correlates of these sexual interactions include long-term cellular changes in dopamine transmission and postsynaptic signaling pathways related to neuronal plasticity (e.g., dendritic spine formation). Taken together, these studies suggest that sexual experience enhances the reinforcing properties of sexual behavior, which has the coincident outcome of increasing copulatory efficiency in a way that can increase reproductive success. PMID:16978593

Strain-controlled fatigue behaviors of porous PLA-based scaffolds by 3D-printing technology.

PubMed

Gong, Baoming; Cui, Shaohua; Zhao, Yun; Sun, Yongtao; Ding, Qian

2017-12-01

In the study, the low-cycle fatigue behaviors of 3D-printed poly lactic acid (PLA) scaffolds with 60% porosity and two kinds of geometrical pores were investigated under strain-controlled loading. The obtained Δε a -N f curves were fitted by Coffin-Manson relation. The mechanical stability of the porous structure under cyclic loading was studied. Both kinds of specimens undergo the strain softening after the initial cyclic hardening. The scaffold with circular pore exhibits stable resistance to the fatigue damage which is desirable for bone repairing. Regarding to the accumulation of inelastic deformation, the triangular-scaffold is more sensitive to the cyclic load. The superior fatigue behaviors of the scaffold with circular pore is attributed to homogeneous distribution of the applied mechanical stress and diminishing stress concentration by the introduction of circular pore.

Harassment of adults by immatures in bonobos (Pan paniscus): testing the Exploratory Aggression and Rank Improvement hypotheses.

PubMed

Boose, Klaree; White, Frances

2017-10-01

The immatures of many primate species frequently pester adult group members with aggressive behaviors referred to as a type of harassment. Although these behaviors are characteristic of immatures as they develop from infancy through adolescence, there have been few studies that specifically address the adaptive significance of harassment. Two functional hypotheses have been generated from observations of the behavior in chimpanzees. The Exploratory Aggression hypothesis describes harassment as a mechanism used by immatures to learn about the parameters of aggression and dominance behavior and to acquire information about novel, complex, or unpredictable relationships. The Rank Improvement hypothesis describes harassment as a mechanism of dominance acquisition used by immatures to outrank adults. This study investigated harassment of adults by immatures in a group of bonobos housed at the Columbus Zoo and compared the results to the predictions outlined by the Exploratory Aggression and Rank Improvement hypotheses. Although all immature bonobos in this group harassed adults, adolescents performed the behavior more frequently than did infants or juveniles and low-ranking adults were targeted more frequently than high-ranking. Targets responded more with agonistic behaviors than with neutral behaviors and the amount of harassment an individual received was significantly correlated with the amount of agonistic responses given. Furthermore, bouts of harassment were found to continue significantly more frequently when responses were agonistic than when they were neutral. Adolescents elicited mostly agonistic responses from targets whereas infants and juveniles received mostly neutral responses. These results support predictions from each hypothesis where harassment functions both as a mechanism of social exploration and as a tool to establish dominance rank.

Behavioral mechanisms in HIV epidemiology and prevention: past, present, and future roles.

PubMed

Bingenheimer, Jeffrey B; Geronimus, Arline T

2009-09-01

In the 1980s, behavioral variations across geographically and socially defined populations were the central focus of AIDS research, and behavior change was seen as the primary means of controlling HIV epidemics. Today, biological mechanisms--especially other sexually transmitted infections, antiretroviral therapy, and male circumcision--predominate in HIV epidemiology and prevention. We describe several reasons for this shift in emphasis. Although the shift is understandable, we argue for a sustained focus on behavioral mechanisms in HIV research in order to realize the theoretical promise of interventions targeting the biological aspects of HIV risk. We also provide evidence to suggest that large reductions in HIV prevalence may be accomplished by small changes in behavior. Moreover, we contend that behavioral mechanisms will find their proper place in HIV epidemiology and prevention only when investigators adopt a conceptual model that treats prevalence as a determinant as well as an outcome of behavior and that explicitly recognizes the dynamic interdependence between behavior and other epidemiological and demographic parameters.

An overview on the characterization and mechanical behavior of nanoporous Gold

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hodge, A M; Hayes, J R; Caro, J A

2005-09-13

In this paper we present what we believe are the most pressing issues in understanding the mechanical behavior of nanoporous foams. We have postulated that a gold foam presents the best candidate for a systematic study of nanoporous foams since it can be synthesized with a wide range of ligaments sizes and densities. We have also conducted preliminary tests that demonstrate (a) Au foams have a fracture behavior dictated by the ligament size, and (b) nanoporous Au is a high yield strength material. Thus, we have demonstrated the potential in developing nanoporous foams as a new class of high yieldmore » strength/low density materials.« less

Oxytocin modulation of neural circuits for social behavior.

PubMed

Marlin, Bianca J; Froemke, Robert C

2017-02-01

Oxytocin is a hypothalamic neuropeptide that has gained attention for the effects on social behavior. Recent findings shed new light on the mechanisms of oxytocin in synaptic plasticity and adaptively modifying neural circuits for social interactions such as conspecific recognition, pair bonding, and maternal care. Here, we review several of these newer studies on oxytocin in the context of previous findings, with an emphasis on social behavior and circuit plasticity in various brain regions shown to be enriched for oxytocin receptors. We provide a framework that highlights current circuit-level mechanisms underlying the widespread action of oxytocin. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 169-189, 2017. © 2016 Wiley Periodicals, Inc.

[The behavioral-neuroendocrine mechanism of development of homosexuality].

PubMed

Xue, Hui; Tai, Fa-Dao

2007-10-01

In this review, we primarily focus on the behavioral-neuroendocrine mechanism of development of homosexuality from genetic, neuroendocrine neuroanatomical and behavioral studies. Besides the influence of genetics and environment, sexual orientation was determined by the early perinatal hormone exposure. Gonadal steroidal hormone interacted with many neurotransmitters in individual development by hypothalamus pituitary adrenal axis and hypothalamus pituitary gonadal axis, which regulated the individual's sexual orientation. It was summarized here about the future directions on sexual orientation and demonstrated problems which would have to investigate next step. All these may be beneficial for our understanding of the homosexuality and paying attention to psychological and physiological health of homosexuality, which is useful to prevent the development of teenage homosexuality.

Economic Disadvantage and Young Children's Emotional and Behavioral Problems: Mechanisms of Risk

ERIC Educational Resources Information Center

Rijlaarsdam, Jolien; Stevens, Gonneke W. J. M.; van der Ende, Jan; Hofman, Albert; Jaddoe, Vincent W. V.; Mackenbach, Johan P.; Verhulst, Frank C.; Tiemeier, Henning

2013-01-01

This study aimed to establish potential mechanisms through which economic disadvantage contributes to the development of young children's internalizing and externalizing problems. Prospective data from fetal life to age 3 years were collected in a total of 2,169 families participating in the Generation R Study. The observed physical home…

Behavioral and Metabolic Phenotype Indicate Personality in Zebrafish (Danio rerio)

PubMed Central

Yuan, Mingzhe; Chen, Yan; Huang, Yingying; Lu, Weiqun

2018-01-01

Consistency of individual differences of animal behavior and personality in reactions to various environmental stresses among their life stages could reflect basic divergences in coping style which may affect survival, social rank, and reproductive success in the wild. However, the physiological mechanisms determining personality remain poorly understood. In order to study whether behavior, metabolism and physiological stress responses relate to the personality, we employed post-stress recovery assays to separate zebrafish into two behavioral types (proactive and reactive). The results demonstrated consistent difference among personality, behavior and metabolism in which proactive individuals were more aggressive, had higher standard metabolic rates and showed lower shuttled frequencies between dark and light compartments than the reactive ones. The behavioral variations were also linked to divergent acute salinity stress responses: proactive individuals adopted a swift locomotion behavior in response to acute salinity challenge while reactive individuals remain unchanged. Our results provide useful insight into how personality acts on correlated traits and the importance of a holistic approach to understanding the mechanisms driving persistent inter-individual differences. PMID:29899710

Anyone Can Become a Troll: Causes of Trolling Behavior in Online Discussions.

PubMed

Cheng, Justin; Bernstein, Michael; Danescu-Niculescu-Mizil, Cristian; Leskovec, Jure

2017-01-01

In online communities, antisocial behavior such as trolling disrupts constructive discussion. While prior work suggests that trolling behavior is confined to a vocal and antisocial minority, we demonstrate that ordinary people can engage in such behavior as well. We propose two primary trigger mechanisms: the individual's mood, and the surrounding context of a discussion (e.g., exposure to prior trolling behavior). Through an experiment simulating an online discussion, we find that both negative mood and seeing troll posts by others significantly increases the probability of a user trolling, and together double this probability. To support and extend these results, we study how these same mechanisms play out in the wild via a data-driven, longitudinal analysis of a large online news discussion community. This analysis reveals temporal mood effects, and explores long range patterns of repeated exposure to trolling. A predictive model of trolling behavior shows that mood and discussion context together can explain trolling behavior better than an individual's history of trolling. These results combine to suggest that ordinary people can, under the right circumstances, behave like trolls.

Anyone Can Become a Troll: Causes of Trolling Behavior in Online Discussions

PubMed Central

Cheng, Justin; Bernstein, Michael; Danescu-Niculescu-Mizil, Cristian; Leskovec, Jure

2018-01-01

In online communities, antisocial behavior such as trolling disrupts constructive discussion. While prior work suggests that trolling behavior is confined to a vocal and antisocial minority, we demonstrate that ordinary people can engage in such behavior as well. We propose two primary trigger mechanisms: the individual’s mood, and the surrounding context of a discussion (e.g., exposure to prior trolling behavior). Through an experiment simulating an online discussion, we find that both negative mood and seeing troll posts by others significantly increases the probability of a user trolling, and together double this probability. To support and extend these results, we study how these same mechanisms play out in the wild via a data-driven, longitudinal analysis of a large online news discussion community. This analysis reveals temporal mood effects, and explores long range patterns of repeated exposure to trolling. A predictive model of trolling behavior shows that mood and discussion context together can explain trolling behavior better than an individual’s history of trolling. These results combine to suggest that ordinary people can, under the right circumstances, behave like trolls. PMID:29399664

Acousto-optical assessment of skin viscoelasticity

NASA Astrophysics Data System (ADS)

Kirkpatrick, Sean J.; Duncan, Donald D.

2003-07-01

A multiphysics approach, combining acoustics, optics, and mechanics can be used to detect regions of skin with distinct mechanical behavior that may indicate a pathology, such as a cancerous skin lesion. Herein, an acousto-optical approach to evaluating the viscoelastic behavior of superficial skin layers will be presented. The method relies upon inducing low frequency guided surface waves in the skin and detecting these waves by monitoring the shift in the backscattered laser speckle pattern created by illuminating a small region of the skin with coherent light. Artificial lesions in the form of chemical cross-linking and chemical softening were induced in superficial porcine skin layers and detected based upon variations in local mechanical behavior. The lesions affect not only the time-of-flight of the guided surface waves, but also change the relative phase of the acoustic waves as determined optically. The method may be applicable in the study and diagnosis of superficial skin lesions.

Sleep Duration and Diabetes Risk: Population Trends and Potential Mechanisms

PubMed Central

Grandner, Michael A.; Seixas, Azizi; Shetty, Safal; Shenoy, Sundeep

2016-01-01

Sleep is important for regulating many physiologic functions that relate to metabolism. Because of this, there is substantial evidence to suggest that sleep habits and sleep disorders are related to diabetes risk. In specific, insufficient sleep duration and/or sleep restriction in the laboratory, poor sleep quality, and sleep disorders such as insomnia and sleep apnea have all been associated with diabetes risk. This research spans epidemiologic and laboratory studies. Both physiologic mechanisms such as insulin resistance, decreased leptin, and increased ghrelin and inflammation and behavioral mechanisms such as increased food intake, impaired decision-making, and increased likelihood of other behavioral risk factors such as smoking, sedentary behavior, and alcohol use predispose to both diabetes and obesity, which itself is an important diabetes risk factor. This review describes the evidence linking sleep and diabetes risk at the population and laboratory levels. PMID:27664039

A Behavioral Mechanism of How Increases in Leg Strength Improve Old Adults’ Gait Speed

PubMed Central

Uematsu, Azusa; Tsuchiya, Kazushi; Kadono, Norio; Kobayashi, Hirofumi; Kaetsu, Takamasa; Hortobágyi, Tibor; Suzuki, Shuji

2014-01-01

We examined a behavioral mechanism of how increases in leg strength improve healthy old adults’ gait speed. Leg press strength training improved maximal leg press load 40% (p = 0.001) and isometric strength in 5 group of leg muscles 32% (p = 0.001) in a randomly allocated intervention group of healthy old adults (age 74, n = 15) but not in no-exercise control group (age 74, n = 8). Gait speed increased similarly in the training (9.9%) and control (8.6%) groups (time main effect, p = 0.001). However, in the training group only, in line with the concept of biomechanical plasticity of aging gait, hip extensors and ankle plantarflexors became the only significant predictors of self-selected and maximal gait speed. The study provides the first behavioral evidence regarding a mechanism of how increases in leg strength improve healthy old adults’ gait speed. PMID:25310220

Are the same tapes really the same? Ultrasound study of laser-cut and mechanically cut TVT-O post-operative behavior.

PubMed

Rusavy, Zdenek; Masata, Jaromir; Svabik, Kamil; Hubka, Petr; Zvara, Karel; Martan, Alois

2017-11-25

TVT-O production has been modified to laser cutting from mechanical cutting. We compared the behavior of laser and mechanically cut tension-free vaginal tape-obturator (TVT-O) using ultrasound at various time points after surgery. This is a retrospective analysis of clinical and ultrasound data from two previously reported randomized controlled trials with TVT-O. Behavior of mechanically cut TVT-O implanted in January 2007 to November 2009 and laser-cut TVT-O implanted in May 2010 to May 2012 was assessed by ultrasound at day 1, the 2nd week, the 3rd month, and the 1st and 2nd years post-operatively. Bladder neck and tape margins positions were described by coordinates in the orthogonal system calculated from polar coordinates. Tape mobility was measured as a change in the upper and lower tape margin position from rest to maximal Valsalva. Comparison of 2-year subjective and objective surgery outcomes was also performed. In total, 68 mechanically cut and 50 laser-cut TVT-Os were implanted. Follow-up data were available from 49 and 45 women respectively. No differences in any baseline characteristics or bladder neck mobility were observed. Significantly lower tape mobility was observed on day 1 and week 2 after mechanically cut TVT-O, although subsequent mobility was comparable to laser-cut TVT-O. The subjective and objective surgery outcomes were comparable. Although without clinical significance, early postoperative behavior of the mechanically cut and laser-cut TVT-O tapes differs. The less stiff, mechanically-cut TVT-O loosens within 2 weeks of implantation, whereas the stiffer, laser-cut TVT-O keeps its tension.

Hormones and the Evolution of Complex Traits: Insights from Artificial Selection on Behavior

PubMed Central

Garland, Theodore; Zhao, Meng; Saltzman, Wendy

2016-01-01

Although behavior may often be a fairly direct target of natural or sexual selection, it cannot evolve without changes in subordinate traits that cause or permit its expression. In principle, changes in endocrine function could be a common mechanism underlying behavioral evolution because they are well positioned to mediate integrated responses to behavioral selection. More specifically, hormones can influence both motivational (e.g., brain) and performance (e.g., muscles) components of behavior simultaneously and in a coordinated fashion. If the endocrine system is often “used” as a general mechanism to effect responses to selection, then correlated responses in other aspects of behavior, life history, and organismal performance (e.g., locomotor abilities) should commonly occur because any cell with appropriate receptors could be affected. Ways in which behavior coadapts with other aspects of the phenotype can be studied directly through artificial selection and experimental evolution. Several studies have targeted rodent behavior for selective breeding and reported changes in other aspects of behavior, life history, and lower-level effectors of these organismal traits, including endocrine function. One example involves selection for high levels of voluntary wheel running, one aspect of physical activity, in four replicate High Runner (HR) lines of mice. Circulating levels of several hormones (including insulin, testosterone, thyroxine, triiodothyronine) have been characterized, three of which—corticosterone, leptin, and adiponectin—differ between HR and control lines, depending on sex, age, and generation. Potential changes in circulating levels of other behaviorally and metabolically relevant hormones, as well as in other components of the endocrine system (e.g., receptors), have yet to be examined. Overall, results to date identify promising avenues for further studies on the endocrine basis of activity levels. PMID:27252193

Successful Training of Filtering Mechanisms in Multiple Object Tracking Does Not Transfer to Filtering Mechanisms in a Visual Working Memory Task: Behavioral and Electrophysiological Evidence

ERIC Educational Resources Information Center

Arend, Anna M.; Zimmer, Hubert D.

2012-01-01

In this training study, we aimed to selectively train participants' filtering mechanisms to enhance visual working memory (WM) efficiency. The highly restricted nature of visual WM capacity renders efficient filtering mechanisms crucial for its successful functioning. Filtering efficiency in visual WM can be measured via the lateralized change…

Contribution of collagen and elastin fibers to the mechanical behavior of an abdominal connective tissue.

PubMed

Levillain, A; Orhant, M; Turquier, F; Hoc, T

2016-08-01

The linea alba is a complex structure commonly involved in hernia formation. Knowledge of its mechanical behavior is essential to design suitable meshes and reduce the risk of recurrence. The aim of this study was to investigate the relationships between the mechanical properties of the linea alba and the organization of collagen and elastin fibers. For that purpose, longitudinal and transversal samples were removed from four porcine and three human linea alba, to perform tensile tests under a biphotonic confocal microscope, in each direction. Microscopic observation revealed a tissue composed of two layers, made of transversal collagen fibers in the dorsal side and oblique collagen fibers in the ventral side. This particular architecture led to an anisotropic mechanical behavior, with higher stress in the transversal direction. During loading, oblique fibers of the ventral layer reoriented toward the tensile axis in both directions, while fibers of the dorsal layer remained in the transversal direction. This rotation of oblique fibers progressively increased the stiffness of the tissue and induced a non-linear stress-stretch relation. Elastin fibers formed a layer covering the collagen fibers and followed their movement, suggesting that they ensure their elastic recoil. All of these results demonstrated the strong relationships between the microstructure and the mechanical behavior of the linea alba. Copyright © 2016 Elsevier Ltd. All rights reserved.

Review of Corrosion Fatigue.

DTIC Science & Technology

1981-11-16

other is not always well defined. 3.0 CORROSIM FATIGUE VARIABLES AND THEIR EFFECTS Corrosion fatigue behavior is pverned, y Ir of variables- environmental...on near threshold fatigue crack growth behavior is primarily a function of environmental reaction in this steel . 3.2 Mechanical Effects Among the...Gallagher""’ and Pao studied the corrosion fatigue behavior of 4340 steel at various * Ifrequencies in distilled water and water vapor, respectively

Sensory Gain Outperforms Efficient Readout Mechanisms in Predicting Attention-Related Improvements in Behavior

PubMed Central

Ester, Edward F.; Deering, Sean

2014-01-01

Spatial attention has been postulated to facilitate perceptual processing via several different mechanisms. For instance, attention can amplify neural responses in sensory areas (sensory gain), mediate neural variability (noise modulation), or alter the manner in which sensory signals are selectively read out by postsensory decision mechanisms (efficient readout). Even in the context of simple behavioral tasks, it is unclear how well each of these mechanisms can account for the relationship between attention-modulated changes in behavior and neural activity because few studies have systematically mapped changes between stimulus intensity, attentional focus, neural activity, and behavioral performance. Here, we used a combination of psychophysics, event-related potentials (ERPs), and quantitative modeling to explicitly link attention-related changes in perceptual sensitivity with changes in the ERP amplitudes recorded from human observers. Spatial attention led to a multiplicative increase in the amplitude of an early sensory ERP component (the P1, peaking ∼80–130 ms poststimulus) and in the amplitude of the late positive deflection component (peaking ∼230–330 ms poststimulus). A simple model based on signal detection theory demonstrates that these multiplicative gain changes were sufficient to account for attention-related improvements in perceptual sensitivity, without a need to invoke noise modulation. Moreover, combining the observed multiplicative gain with a postsensory readout mechanism resulted in a significantly poorer description of the observed behavioral data. We conclude that, at least in the context of relatively simple visual discrimination tasks, spatial attention modulates perceptual sensitivity primarily by modulating the gain of neural responses during early sensory processing PMID:25274817

Young Adult Risk Factors for Cancer: Obesity, Inflammation, and Sociobehavioral Mechanisms.

PubMed

Yang, Yang Claire; Johnson, Moira P; Schorpp, Kristen M; Boen, Courtney E; Harris, Kathleen Mullan

2017-09-01

The paper assesses social disparities in the burdens of metabolic and inflammatory risks for cancer in the U.S. young adult population and examines psychosocial and behavioral mechanisms in such disparities. Using data of 7,889 individuals aged 12-32 years from the National Longitudinal Study of Adolescent to Adult Health from 1994 to 2009, generalized linear models were used to assess the sex, race/ethnicity, and SES differences in the risks of obesity and inflammation, measured by C-reactive protein. Further tests examined the extent to which social isolation, smoking, physical inactivity, alcohol abuse, and illicit drug use explain social differentials in each biomarker outcome. Women, blacks, Hispanics, and socioeconomically disadvantaged groups had higher risks of obesity and elevated C-reactive protein, with the SES gradients being more pronounced in female participants. Health-related behaviors showed large variation across sex, race, and SES strata. After adjusting for these behavioral variables, sex, and race disparities in obesity and excess inflammation in blacks diminished, whereas the adolescent SES disparity in obesity remained. The associations of adolescent and young adult SES disadvantage and inflammation were also explained by behavioral mechanisms. Behavioral factors associated with higher risks of obesity and inflammation differed, with the exception of fast food consumption, a risk factor for both. This study provides new knowledge of social distribution of early life exposures to physiologic precedents to cancer development later in life with implications for prevention and early intervention of modifiable risky behaviors in adolescents and young adults. Copyright © 2017 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.

Cognitive Model of Trust Dynamics Predicts Human Behavior within and between Two Games of Strategic Interaction with Computerized Confederate Agents

PubMed Central

Collins, Michael G.; Juvina, Ion; Gluck, Kevin A.

2016-01-01

When playing games of strategic interaction, such as iterated Prisoner's Dilemma and iterated Chicken Game, people exhibit specific within-game learning (e.g., learning a game's optimal outcome) as well as transfer of learning between games (e.g., a game's optimal outcome occurring at a higher proportion when played after another game). The reciprocal trust players develop during the first game is thought to mediate transfer of learning effects. Recently, a computational cognitive model using a novel trust mechanism has been shown to account for human behavior in both games, including the transfer between games. We present the results of a study in which we evaluate the model's a priori predictions of human learning and transfer in 16 different conditions. The model's predictive validity is compared against five model variants that lacked a trust mechanism. The results suggest that a trust mechanism is necessary to explain human behavior across multiple conditions, even when a human plays against a non-human agent. The addition of a trust mechanism to the other learning mechanisms within the cognitive architecture, such as sequence learning, instance-based learning, and utility learning, leads to better prediction of the empirical data. It is argued that computational cognitive modeling is a useful tool for studying trust development, calibration, and repair. PMID:26903892

Language Learning Enhanced by Massive Multiple Online Role-Playing Games (MMORPGs) and the Underlying Behavioral and Neural Mechanisms.

PubMed

Zhang, Yongjun; Song, Hongwen; Liu, Xiaoming; Tang, Dinghong; Chen, Yue-E; Zhang, Xiaochu

2017-01-01

Massive Multiple Online Role-Playing Games (MMORPGs) have increased in popularity among children, juveniles, and adults since MMORPGs' appearance in this digital age. MMORPGs can be applied to enhancing language learning, which is drawing researchers' attention from different fields and many studies have validated MMORPGs' positive effect on language learning. However, there are few studies on the underlying behavioral or neural mechanism of such effect. This paper reviews the educational application of the MMORPGs based on relevant macroscopic and microscopic studies, showing that gamers' overall language proficiency or some specific language skills can be enhanced by real-time online interaction with peers and game narratives or instructions embedded in the MMORPGs. Mechanisms underlying the educational assistant role of MMORPGs in second language learning are discussed from both behavioral and neural perspectives. We suggest that attentional bias makes gamers/learners allocate more cognitive resources toward task-related stimuli in a controlled or an automatic way. Moreover, with a moderating role played by activation of reward circuit, playing the MMORPGs may strengthen or increase functional connectivity from seed regions such as left anterior insular/frontal operculum (AI/FO) and visual word form area to other language-related brain areas.

Modeling the heterogeneity of human dynamics based on the measurements of influential users in Sina Microblog

NASA Astrophysics Data System (ADS)

Wang, Chenxu; Guan, Xiaohong; Qin, Tao; Yang, Tao

2015-06-01

Online social network has become an indispensable communication tool in the information age. The development of microblog also provides us a great opportunity to study human dynamics that play a crucial role in the design of efficient communication systems. In this paper we study the characteristics of the tweeting behavior based on the data collected from Sina Microblog. The user activity level is measured to characterize how often a user posts a tweet. We find that the user activity level follows a bimodal distribution. That is, the microblog users tend to be either active or inactive. The inter-tweeting time distribution is then measured at both the aggregate and individual levels. We find that the inter-tweeting time follows a piecewise power law distribution of two tails. Furthermore, the exponents of the two tails have different correlations with the user activity level. These findings demonstrate that the dynamics of the tweeting behavior are heterogeneous in different time scales. We then develop a dynamic model co-driven by the memory and the interest mechanism to characterize the heterogeneity. The numerical simulations validate the model and verify that the short time interval tweeting behavior is driven by the memory mechanism while the long time interval behavior by the interest mechanism.

Analgesics as Reinforcers with Chronic Pain: Evidence from Operant Studies

PubMed Central

Ewan, Eric E.; Martin, Thomas J.

2013-01-01

Previously preclinical pain research has focused on simple behavioral endpoints to assess the efficacy of analgesics in acute and chronic pain models, primarily reflexive withdrawal from an applied mechanical or thermal stimulus. However recent research has been aimed at investigating other behavioral states in the presence of pain, including spontaneous, non-elicited pain. One approach is to investigate the reinforcing effects of analgesics in animals with experimental pain, which should serve as reinforcers by virtue of their ability to alleviate the relevant subjective states induced by pain. The gold standard for assessing drug reinforcement is generally accepted to be drug self-administration, and this review highlights the ability of drugs to serve as reinforcers in animals with experimental neuropathic pain, and the extent to which this behavior is altered in chronic pain states. Additionally, intracranial self-stimulation is an operant procedure that has been used extensively to study drug reinforcement mechanisms and the manner in which neuropathic pain alters the ability of drugs to serve as reinforcers in this paradigm will also be discussed. Drug self-administration and intracranial self-stimulation have promise as tools to investigate behavioral effects of analgesics in animals with chronic pain, particularly regarding the mechanisms through which these drugs motivate consumption in a chronic pain state. PMID:23973302

What the laboratory rat has taught us about social play behavior: role in behavioral development and neural mechanisms.

PubMed

Vanderschuren, Louk J M J; Trezza, Viviana

2014-01-01

Social play behavior is the most vigorous and characteristic form of social interaction displayed by developing mammals. The laboratory rat is an ideal species to study this behavior, since it shows ample social play that can be easily recognized and quantified. In this chapter, we will first briefly describe the structure of social play behavior in rats. Next, we will discuss studies that used social isolation rearing during the period in life when social play is most abundant to investigate the developmental functions of social play behavior in rats, focusing on the consequences of play deprivation on social, cognitive, emotional, and sensorimotor development. Last, we will discuss the neural substrates of social play behavior in rats, with emphasis on the limbic corticostriatal circuits that underlie emotions and their influence on behavior.

Crystallization behavior of polyamide-6 microcellular nanocomposites

Treesearch

Mingjun Yuan; Lih-Sheng Turng; Shaoqin Gong; Andreas Winardi

2004-09-01

The crystallization behaviors of polyamide-6 (PA-6) and its nanocomposites undergoing the microcellular injection molding process are studied using Transmission Electron Microscopy (TEM), X-ray Diffractometer (XRD), Polarized Optical Microscopy (POM), and Differential Scanning Calorimetry (DSC). The relationships among the morphology, the mechanical property of the...

Behavior analysis and mechanism: One is not the other

PubMed Central

Morris, Edward K.

1993-01-01

Behavior analysts have been called mechanists, and behavior analysis is said to be mechanistic; that is, they are claimed to be aligned with the philosophy of mechanism. What this means is analyzed by (a) examining standard and specialized dictionary and encyclopedia definitions and descriptions of mechanism and its cognates and (b) reviewing contemporary representations of the mechanistic worldview in the literature on the philosophy of psychology. Although the term mechanism and its cognates are sometimes an honorific (e.g., “natural science”), their standard meanings, usages, and functions in society, science, psychology, and philosophy do not aptly characterize the discipline. These terms mischaracterize how behavior analysts conceptualize (a) the behavior of their subjects and the individuals with whom they work and (b) their own behavior as scientists. Discussion is interwoven throughout about the nature of terms and definitions in science. PMID:22478129

The Organization of Behavior Over Time: Insights from Mid-Session Reversal

PubMed Central

Rayburn-Reeves, Rebecca M.; Cook, Robert G.

2016-01-01

What are the mechanisms by which behavior is organized sequentially over time? The recently developed mid-session reversal (MSR) task offers new insights into this fundamental question. The typical MSR task is arranged to have a single reversed discrimination occurring in a consistent location within each session and across sessions. In this task, we examine the relevance of time, reinforcement, and other factors as the switching cue in the sequential modulation of control in MSR. New analyses also highlight some of the potential mechanisms underlying this serially organized behavior. MSR provides new evidence and we offer some ideas about how cues interact to compete for the control of behavior within and across sessions. We suggest that MSR is an excellent preparation for studying the competition among psychological states and their resolution toward action. PMID:27942272

The Organization of Behavior Over Time: Insights from Mid-Session Reversal.

PubMed

Rayburn-Reeves, Rebecca M; Cook, Robert G

2016-01-01

What are the mechanisms by which behavior is organized sequentially over time? The recently developed mid-session reversal (MSR) task offers new insights into this fundamental question. The typical MSR task is arranged to have a single reversed discrimination occurring in a consistent location within each session and across sessions. In this task, we examine the relevance of time, reinforcement, and other factors as the switching cue in the sequential modulation of control in MSR. New analyses also highlight some of the potential mechanisms underlying this serially organized behavior. MSR provides new evidence and we offer some ideas about how cues interact to compete for the control of behavior within and across sessions. We suggest that MSR is an excellent preparation for studying the competition among psychological states and their resolution toward action.

Impulsive behavior and nicotinic acetylcholine receptors.

PubMed

Ohmura, Yu; Tsutsui-Kimura, Iku; Yoshioka, Mitsuhiro

2012-01-01

Higher impulsivity is thought to be a risk factor for drug addiction, criminal involvement, and suicide. Excessive levels of impulsivity are often observed in several psychiatric disorders including attention-deficit/hyperactivity disorder and schizophrenia. Previous studies have demonstrated that nicotinic acetylcholine receptors (nAChRs) are involved in impulsive behavior. Here, we introduce recent advances in this field and describe the role of the following nAChR-related brain mechanisms in modulating impulsive behavior: dopamine release in the ventral striatum; α4β2 nAChRs in the infralimbic cortex, which is a ventral part of the medial prefrontal cortex (mPFC); and dopamine release in the mPFC. We also suggest several potential therapeutic drugs to address these mechanisms in impulsivity-related disorders and explore future directions to further elucidate the roles of central nAChRs in impulsive behavior.

Thermo-mechanical behavior of power electronic packaging assemblies: From characterization to predictive simulation of lifetimes

NASA Astrophysics Data System (ADS)

Dalverny, O.; Alexis, J.

2018-02-01

This article deals with thermo-mechanical behavior of power electronic modules used in several transportation applications as railway, aeronautic or automotive systems. Due to a multi-layered structures, involving different materials with a large variation of coefficient of thermal expansion, temperature variations originated from active or passive cycling (respectively from die dissipation or environmental constraint) induces strain and stresses field variations, giving fatigue phenomenon of the system. The analysis of the behavior of these systems and their dimensioning require the implementation of complex modeling strategies by both the multi-physical and the multi-scale character of the power modules. In this paper we present some solutions for studying the thermomechanical behavior of brazed assemblies as well as taking into account the interfaces represented by the numerous metallizations involved in the process assembly.

Experimental study on dynamic mechanical behaviors of polycarbonate

NASA Astrophysics Data System (ADS)

Zhang, Wei; Gao, Yubo; Ye, Nan; Huang, Wei; Li, Dacheng

2017-01-01

Polycarbonate (PC) is a widely used engineering material in aerospace field, since it has excellent mechanical and optical property. In present study, both compressive and tensile tests of PC were conducted at high strain rates by using a split Hopkinson pressure bar. The high-speed camera and 2D Digital Image Correlation method (DIC) were used to analyze the dynamic deformation behavior of PC. Meanwhile, the plate impact experiment was carried out to measure the equation of state of PC in a single-stage gas gun, which consists of asymmetric impact technology, manganin gauges, PVDF, electromagnetic particle velocity gauges. The results indicate that the yield stress of PC increased with the strain rates in both dynamic compression and tension tests. The same phenomenon was similar to elasticity modulus at different strain rate. A constitutive model was used to describe the mechanical behaviors of PC accurately in different strain rates by contrast with the results of 2D-DIC. At last, The D-u Hugoniot curve of polycarbonate in high pressure was fitted by the least square method.

TAAR1 in Addiction: Looking Beyond the Tip of the Iceberg

PubMed Central

Liu, Jian-Feng; Li, Jun-Xu

2018-01-01

Trace-amine associated receptor 1 (TAAR1) is the best-characterized member of the family of TAARs. TAAR1 is broadly expressed in the brain, especially within the monoaminergic systems. Evidence from electrophysiological and neurochemical studies evaluating the effects of genetic and pharmacological interventions on TAAR1 revealed that TAAR1 modulates transmission of monoamines, especially dopamine. TAAR1 agonists dampened drugs of abuse-induced dopamine accumulation. In general, TAAR1 agonists specifically inhibited the rewarding and reinforcing effects of drugs of abuse and drug-abuse related behaviors. Details of the mechanism of TAAR1 remain elusive; however, it is thought to be regulated by its interactions with D2 receptors. In addition, the alternative cellular mechanism such as an interaction between TAAR1 and D3 may also participate in the action of TAAR1 agonists. Further studies are required to investigate the role of TAAR1 in other drugs of abuse-related behaviors and the underlying neural mechanisms. Collectively, TAAR1 negatively modulates dopaminergic systems and dopamine-related behaviors and TAAR1 agonists are promising pharmacotherapy to treat drug addiction and relapse. PMID:29636691

Aversive pavlovian responses affect human instrumental motor performance.

PubMed

Rigoli, Francesco; Pavone, Enea Francesco; Pezzulo, Giovanni

2012-01-01

IN NEUROSCIENCE AND PSYCHOLOGY, AN INFLUENTIAL PERSPECTIVE DISTINGUISHES BETWEEN TWO KINDS OF BEHAVIORAL CONTROL: instrumental (habitual and goal-directed) and Pavlovian. Understanding the instrumental-Pavlovian interaction is fundamental for the comprehension of decision-making. Animal studies (as those using the negative auto-maintenance paradigm), have demonstrated that Pavlovian mechanisms can have maladaptive effects on instrumental performance. However, evidence for a similar effect in humans is scarce. In addition, the mechanisms modulating the impact of Pavlovian responses on instrumental performance are largely unknown, both in human and non-human animals. The present paper describes a behavioral experiment investigating the effects of Pavlovian conditioned responses on performance in humans, focusing on the aversive domain. Results showed that Pavlovian responses influenced human performance, and, similar to animal studies, could have maladaptive effects. In particular, Pavlovian responses either impaired or increased performance depending on modulator variables such as threat distance, task controllability, punishment history, amount of training, and explicit punishment expectancy. Overall, these findings help elucidating the computational mechanisms underlying the instrumental-Pavlovian interaction, which might be at the base of apparently irrational phenomena in economics, social behavior, and psychopathology.

Aversive Pavlovian Responses Affect Human Instrumental Motor Performance

PubMed Central

Rigoli, Francesco; Pavone, Enea Francesco; Pezzulo, Giovanni

2012-01-01

In neuroscience and psychology, an influential perspective distinguishes between two kinds of behavioral control: instrumental (habitual and goal-directed) and Pavlovian. Understanding the instrumental-Pavlovian interaction is fundamental for the comprehension of decision-making. Animal studies (as those using the negative auto-maintenance paradigm), have demonstrated that Pavlovian mechanisms can have maladaptive effects on instrumental performance. However, evidence for a similar effect in humans is scarce. In addition, the mechanisms modulating the impact of Pavlovian responses on instrumental performance are largely unknown, both in human and non-human animals. The present paper describes a behavioral experiment investigating the effects of Pavlovian conditioned responses on performance in humans, focusing on the aversive domain. Results showed that Pavlovian responses influenced human performance, and, similar to animal studies, could have maladaptive effects. In particular, Pavlovian responses either impaired or increased performance depending on modulator variables such as threat distance, task controllability, punishment history, amount of training, and explicit punishment expectancy. Overall, these findings help elucidating the computational mechanisms underlying the instrumental-Pavlovian interaction, which might be at the base of apparently irrational phenomena in economics, social behavior, and psychopathology. PMID:23060738

The Ecology of Exercise: Mechanisms Underlying Individual Variation in Behavior, Activity, and Performance: An Introduction to Symposium.

PubMed

Killen, Shaun S; Calsbeek, Ryan; Williams, Tony D

2017-08-01

Wild animals often engage in intense physical activity while performing tasks vital for their survival and reproduction associated with foraging, avoiding predators, fighting, providing parental care, and migrating. In this theme issue we consider how viewing these tasks as "exercise"-analogous to that performed by human athletes-may help provide insight into the mechanisms underlying individual variation in these types of behaviors and the importance of physical activity in an ecological context. In this article and throughout this issue, we focus on four key questions relevant to the study of behavioral ecology that may be addressed by studying wild animal behavior from the perspective of exercise physiology: (1) How hard do individual animals work in response to ecological (or evolutionary) demands?; (2) Do lab-based studies of activity provide good models for understanding activity in free-living animals and individual variation in traits?; (3) Can animals work too hard during "routine" activities?; and (4) Can paradigms of "exercise" and "training" be applied to free-living animals? Attempts to address these issues are currently being facilitated by rapid technological developments associated with physiological measurements and the remote tracking of wild animals, to provide mechanistic insights into the behavior of free-ranging animals at spatial and temporal scales that were previously impossible. We further suggest that viewing the behaviors of non-human animals in terms of the physical exercise performed will allow us to fully take advantage of these technological advances, draw from knowledge and conceptual frameworks already in use by human exercise physiologists, and identify key traits that constrain performance and generate variation in performance among individuals. It is our hope that, by highlighting mechanisms of behavior and performance, the articles in this issue will spur on further synergies between physiologists and ecologists, to take advantage of emerging cross-disciplinary perspectives and technologies. © The Author 2017. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology.

The coupled bio-chemo-electro-mechanical behavior of glucose exposed arterial elastin

NASA Astrophysics Data System (ADS)

Zhang, Yanhang; Li, Jiangyu; Boutis, Gregory S.

2017-04-01

Elastin, the principle protein component of the elastic fiber, is a critical extracellular matrix (ECM) component of the arterial wall providing structural resilience and biological signaling essential in vascular morphogenesis and maintenance of mechanical homeostasis. Pathogenesis of many cardiovascular diseases have been associated with alterations of elastin. As a long-lived ECM protein that is deposited and organized before adulthood, elastic fibers can suffer from cumulative effects of biochemical exposure encountered during aging and/or disease, which greatly compromise their mechanical function. This review article covers findings from recent studies of the mechanical and structural contribution of elastin to vascular function, and the effects of biochemical degradation. Results from diverse experimental methods including tissue-level mechanical characterization, fiber-level nonlinear optical imaging, piezoelectric force microscopy, and nuclear magnetic resonance are reviewed. The intriguing coupled bio-chemo-electro-mechanical behavior of elastin calls for a multi-scale and multi-physical understanding of ECM mechanics and mechanobiology in vascular remodeling.

Upregulation of Ih expressed in IB4-negative Aδ nociceptive DRG neurons contributes to mechanical hypersensitivity associated with cervical radiculopathic pain

PubMed Central

Liu, Da-Lu; Lu, Na; Han, Wen-Juan; Chen, Rong-Gui; Cong, Rui; Xie, Rou-Gang; Zhang, Yu-Fei; Kong, Wei-Wei; Hu, San-Jue; Luo, Ceng

2015-01-01

Cervical radiculopathy represents aberrant mechanical hypersensitivity. Primary sensory neuron’s ability to sense mechanical force forms mechanotransduction. However, whether this property undergoes activity-dependent plastic changes and underlies mechanical hypersensitivity associated with cervical radiculopathic pain (CRP) is not clear. Here we show a new CRP model producing stable mechanical compression of dorsal root ganglion (DRG), which induces dramatic behavioral mechanical hypersensitivity. Amongst nociceptive DRG neurons, a mechanically sensitive neuron, isolectin B4 negative Aδ-type (IB4− Aδ) DRG neuron displays spontaneous activity with hyperexcitability after chronic compression of cervical DRGs. Focal mechanical stimulation on somata of IB4- Aδ neuron induces abnormal hypersensitivity. Upregulated HCN1 and HCN3 channels and increased Ih current on this subset of primary nociceptors underlies the spontaneous activity together with neuronal mechanical hypersensitivity, which further contributes to the behavioral mechanical hypersensitivity associated with CRP. This study sheds new light on the functional plasticity of a specific subset of nociceptive DRG neurons to mechanical stimulation and reveals a novel mechanism that could underlie the mechanical hypersensitivity associated with cervical radiculopathy. PMID:26577374

Excluded and behaving unethically: social exclusion, physiological responses, and unethical behavior.

PubMed

Kouchaki, Maryam; Wareham, Justin

2015-03-01

Across 2 studies, we investigated the ethical consequences of physiological responses to social exclusion. In Study 1, participants who were socially excluded were more likely to engage in unethical behavior to make money and the level of physiological arousal experienced during exclusion--measured using galvanic skin response--mediated the effects of exclusion on unethical behavior. Likewise, in Study 2, results from a sample of supervisor-subordinate dyads revealed a positive relationship between experience of workplace ostracism and unethical behaviors as rated by the immediate supervisors. This relationship was mediated by employees' reports of experienced physiological arousal. Together, the results of these studies demonstrate that physiological arousal accompanies social exclusion and provides an explanatory mechanism for the increased unethical behavior in both samples. Theoretical implications of these findings for research on ethical behavior and social exclusion in the workplace are discussed. PsycINFO Database Record (c) 2015 APA, all rights reserved.

Choosing an Appropriate Physical Exercise to Reduce Stereotypic Behavior in Children with Autism Spectrum Disorders: A Non-Randomized Crossover Study

ERIC Educational Resources Information Center

Tse, C. Y. Andy; Pang, C. L.; Lee, Paul H.

2018-01-01

Considerable evidence has shown that physical exercise could be an effective treatment in reducing stereotypical autism spectrum disorder (ASD) behaviors in children. The present study seeks to examine the underlying mechanism by considering the theoretical operant nature of stereotypy. Children with ASD (n = 30) who exhibited hand-flapping and…

The Effectiveness Evaluation among Different Player-Matching Mechanisms in a Multi-Player Quiz Game

ERIC Educational Resources Information Center

Tsai, Fu-Hsing

2016-01-01

This study aims to investigate whether different player-matching mechanisms in educational multi-player online games (MOGs) can affect students' learning performance, enjoyment perception and gaming behaviors. Based on the multi-player quiz game, TRIS-Q, developed by Tsai, Tsai and Lin (2015) using a free player-matching (FPM) mechanism, the same…

Menzerath-Altmann Law: Statistical Mechanical Interpretation as Applied to a Linguistic Organization

NASA Astrophysics Data System (ADS)

Eroglu, Sertac

2014-10-01

The distribution behavior described by the empirical Menzerath-Altmann law is frequently encountered during the self-organization of linguistic and non-linguistic natural organizations at various structural levels. This study presents a statistical mechanical derivation of the law based on the analogy between the classical particles of a statistical mechanical organization and the distinct words of a textual organization. The derived model, a transformed (generalized) form of the Menzerath-Altmann model, was termed as the statistical mechanical Menzerath-Altmann model. The derived model allows interpreting the model parameters in terms of physical concepts. We also propose that many organizations presenting the Menzerath-Altmann law behavior, whether linguistic or not, can be methodically examined by the transformed distribution model through the properly defined structure-dependent parameter and the energy associated states.

A plausible neural circuit for decision making and its formation based on reinforcement learning.

PubMed

Wei, Hui; Dai, Dawei; Bu, Yijie

2017-06-01

A human's, or lower insects', behavior is dominated by its nervous system. Each stable behavior has its own inner steps and control rules, and is regulated by a neural circuit. Understanding how the brain influences perception, thought, and behavior is a central mandate of neuroscience. The phototactic flight of insects is a widely observed deterministic behavior. Since its movement is not stochastic, the behavior should be dominated by a neural circuit. Based on the basic firing characteristics of biological neurons and the neural circuit's constitution, we designed a plausible neural circuit for this phototactic behavior from logic perspective. The circuit's output layer, which generates a stable spike firing rate to encode flight commands, controls the insect's angular velocity when flying. The firing pattern and connection type of excitatory and inhibitory neurons are considered in this computational model. We simulated the circuit's information processing using a distributed PC array, and used the real-time average firing rate of output neuron clusters to drive a flying behavior simulation. In this paper, we also explored how a correct neural decision circuit is generated from network flow view through a bee's behavior experiment based on the reward and punishment feedback mechanism. The significance of this study: firstly, we designed a neural circuit to achieve the behavioral logic rules by strictly following the electrophysiological characteristics of biological neurons and anatomical facts. Secondly, our circuit's generality permits the design and implementation of behavioral logic rules based on the most general information processing and activity mode of biological neurons. Thirdly, through computer simulation, we achieved new understanding about the cooperative condition upon which multi-neurons achieve some behavioral control. Fourthly, this study aims in understanding the information encoding mechanism and how neural circuits achieve behavior control. Finally, this study also helps establish a transitional bridge between the microscopic activity of the nervous system and macroscopic animal behavior.

Effects of songs with prosocial lyrics on prosocial behavior: further evidence and a mediating mechanism.

PubMed

Greitemeyer, Tobias

2009-11-01

Previous research has shown that exposure to prosocial songs increased the accessibility of prosocial thoughts, led to more interpersonal empathy, and fostered helping behavior. However, inasmuch as cognition, affect, and behavior were measured in different studies, it remained unclear what variable constituted the mediating path from media exposure to action. This was tested in the present research. In four studies, listening to songs with prosocial, relative to neutral, lyrics increased helping behavior. This effect was mediated by interpersonal empathy. The results are consistent with the general learning model and point to the importance of the affective route in explaining how media exposure influences social behavior.

Research progress on Drosophila visual cognition in China.

PubMed

Guo, AiKe; Zhang, Ke; Peng, YueQin; Xi, Wang

2010-03-01

Visual cognition, as one of the fundamental aspects of cognitive neuroscience, is generally associated with high-order brain functions in animals and human. Drosophila, as a model organism, shares certain features of visual cognition in common with mammals at the genetic, molecular, cellular, and even higher behavioral levels. From learning and memory to decision making, Drosophila covers a broad spectrum of higher cognitive behaviors beyond what we had expected. Armed with powerful tools of genetic manipulation in Drosophila, an increasing number of studies have been conducted in order to elucidate the neural circuit mechanisms underlying these cognitive behaviors from a genes-brain-behavior perspective. The goal of this review is to integrate the most important studies on visual cognition in Drosophila carried out in mainland China during the last decade into a body of knowledge encompassing both the basic neural operations and circuitry of higher brain function in Drosophila. Here, we consider a series of the higher cognitive behaviors beyond learning and memory, such as visual pattern recognition, feature and context generalization, different feature memory traces, salience-based decision, attention-like behavior, and cross-modal leaning and memory. We discuss the possible general gain-gating mechanism implementing by dopamine - mushroom body circuit in fly's visual cognition. We hope that our brief review on this aspect will inspire further study on visual cognition in flies, or even beyond.

Anisotropic Failure Strength of Shale with Increasing Confinement: Behaviors, Factors and Mechanism.

PubMed

Cheng, Cheng; Li, Xiao; Qian, Haitao

2017-11-15

Some studies reported that the anisotropic failure strength of shale will be weakened by increasing confinement. In this paper, it is found that there are various types of anisotropic strength behaviors. Four types of anisotropic strength ratio ( S A 1 ) behaviors and three types of anisotropic strength difference ( S A 2 ) behaviors have been classified based on laboratory experiments on nine groups of different shale samples. The cohesion c w and friction angle ϕ w of the weak planes are proven to be two dominant factors according to a series of bonded-particle discrete element modelling analyses. It is observed that shale is more prone to a slight increase of S A 1 and significant increase of S A 2 with increasing confinement for higher cohesion c w and lower to medium friction angle ϕ w . This study also investigated the mechanism of the anisotropic strength behaviors with increasing confinement. Owing to different contributions of c w and ϕ w under different confinements, different combinations of c w and ϕ w may have various types of influences on the minimum failure strength with the increasing confinement; therefore, different types of anisotropic behaviors occur for different shale specimens as the confinement increases. These findings are very important to understand the stability of wellbore and underground tunneling in the shale rock mass, and should be helpful for further studies on hydraulic fracture propagations in the shale reservoir.

Anisotropic Failure Strength of Shale with Increasing Confinement: Behaviors, Factors and Mechanism

PubMed Central

Cheng, Cheng; Li, Xiao; Qian, Haitao

2017-01-01

Some studies reported that the anisotropic failure strength of shale will be weakened by increasing confinement. In this paper, it is found that there are various types of anisotropic strength behaviors. Four types of anisotropic strength ratio (SA1) behaviors and three types of anisotropic strength difference (SA2) behaviors have been classified based on laboratory experiments on nine groups of different shale samples. The cohesion cw and friction angle ϕw of the weak planes are proven to be two dominant factors according to a series of bonded-particle discrete element modelling analyses. It is observed that shale is more prone to a slight increase of SA1 and significant increase of SA2 with increasing confinement for higher cohesion cw and lower to medium friction angle ϕw. This study also investigated the mechanism of the anisotropic strength behaviors with increasing confinement. Owing to different contributions of cw and ϕw under different confinements, different combinations of cw and ϕw may have various types of influences on the minimum failure strength with the increasing confinement; therefore, different types of anisotropic behaviors occur for different shale specimens as the confinement increases. These findings are very important to understand the stability of wellbore and underground tunneling in the shale rock mass, and should be helpful for further studies on hydraulic fracture propagations in the shale reservoir. PMID:29140292

Mechanisms behind distracted driving behavior: The role of age and executive function in the engagement of distracted driving

PubMed Central

Pope, Caitlin Northcutt; Bell, Tyler Reed; Stavrinos, Despina

2016-01-01

Performing secondary tasks, such as texting while driving, is associated with an increased risk of motor vehicle collisions (MVCs). While cognitive processes, such as executive function, are involved in driving, little is known about the relationship between executive control and willingness to engage in distracted driving. This study investigated the relationship between age, behavioral manifestations of executive function, and self-reported distracted driving behaviors. Executive difficulty (assessed with the BRIEF-A) as well as demographics (age and gender) was considered as possible predictors of engagement in distracted driving behaviors. Fifty-nine young, middle, and older adults self-reported executive difficulty and weekly engagement in distracted driving behaviors. Results revealed that while partially accounted for by age, global executive difficulty was uniquely related to engagement in distracted driving behaviors. Older age was associated with fewer weekly self-reported distracted driving behaviors while higher self-reported executive difficulty was associated with more frequent weekly engagement in distracted behavior. No significant differences were found between young and middle-aged adults on distracted driving behaviors. Findings conclude that distracted driving is a ubiquitous phenomenon evident in drivers of all ages. Possible mechanisms underlying distracted driving behavior could potentially be related to deficits in executive function. PMID:27716494

Mechanisms behind distracted driving behavior: The role of age and executive function in the engagement of distracted driving.

PubMed

Pope, Caitlin Northcutt; Bell, Tyler Reed; Stavrinos, Despina

2017-01-01

Performing secondary tasks, such as texting while driving, is associated with an increased risk of motor vehicle collisions (MVCs). While cognitive processes, such as executive function, are involved in driving, little is known about the relationship between executive control and willingness to engage in distracted driving. This study investigated the relationship between age, behavioral manifestations of executive function, and self-reported distracted driving behaviors. Executive difficulty (assessed with the BRIEF-A) as well as demographics (age and gender) was considered as possible predictors of engagement in distracted driving behaviors. Fifty-nine young, middle, and older adults self-reported executive difficulty and weekly engagement in distracted driving behaviors. Results revealed that while partially accounted for by age, global executive difficulty was uniquely related to engagement in distracted driving behaviors. Older age was associated with fewer weekly self-reported distracted driving behaviors while higher self-reported executive difficulty was associated with more frequent weekly engagement in distracted behavior. No significant differences were found between young and middle-aged adults on distracted driving behaviors. Findings conclude that distracted driving is a ubiquitous phenomenon evident in drivers of all ages. Possible mechanisms underlying distracted driving behavior could potentially be related to deficits in executive function. Copyright © 2016 Elsevier Ltd. All rights reserved.

Imperfect information facilitates the evolution of reciprocity.

PubMed

Kurokawa, Shun

2016-06-01

The existence of cooperation demands explanation since cooperation is costly to the actor. Reciprocity has long been regarded as a potential explanatory mechanism for the existence of cooperation. Reciprocity is a mechanism wherein a cooperator responds to an opponent's behavior by switching his/her own behavior. Hence, a possible problematic case relevant to the theory of reciprocity evolution arises when the mechanism is such that the information regarding an opponent's behavior is imperfect. Although it has been confirmed also by previous theoretical studies that imperfect information interferes with the evolution of reciprocity, this argument is based on the assumption that there are no mistakes in behavior. And, a previous study presumed that it might be expected that when such mistakes occur, reciprocity can more readily evolve in the case of imperfect information than in the case of perfect information. The reason why the previous study considers so is that in the former case, reciprocators can miss defections incurred by other reciprocators' mistakes due to imperfect information, allowing cooperation to persist when such reciprocators meet. However, contrary to this expectation, the previous study has shown that even when mistakes occur, imperfect information interferes with the evolution of reciprocity. Nevertheless, the previous study assumed that payoffs are linear (i.e., that the effect of behavior is additive and there are no synergetic effects). In this study, we revisited the same problem but removed the assumption that payoffs are linear. We used evolutionarily stable strategy analysis to compare the condition for reciprocity to evolve when mistakes occur and information is imperfect with the condition for reciprocity to evolve when mistakes occur and information is perfect. Our study revealed that when payoffs are not linear, imperfect information can facilitate the evolution of reciprocity when mistakes occur; while when payoffs are linear, imperfect information disturbs the evolution of reciprocity even when mistakes occur. Imperfect information can encourage the evolution of cooperation. Copyright © 2016 Elsevier Inc. All rights reserved.

ANNUAL MEETING AMERICAN ORTHOPSYCHIATRIC ASSOCIATION, 40TH. RELEVANCE OF BEHAVIOR THEORY TO DIRECTED LEARNING IN CULTURALLY AND SOCIALLY DISADVANTAGED CHILDREN.

ERIC Educational Resources Information Center

GORDON, EDMUND W.

THE CHOICE OF GOALS AND PRACTICES TO BE UTILIZED IN APPROACHES TO EFFECTING BEHAVIORAL CHANGE IS USUALLY DETERMINED BY THE PRACTITIONER'S VIEW OF THE MECHANISMS UNDERLYING BEHAVIORAL ORGANIZATION. TWO BEHAVIOR THEORIES ARE THE PROJECTIVE VIEW AND THE REFLECTIONAL VIEW OF THE MECHANISMS UNDERLYING BEHAVIORAL ORGANIZATION. IN THE PROJECTIVE VIEW,…

Electrophysiological Correlates of Observational Learning in Children

ERIC Educational Resources Information Center

Rodriguez Buritica, Julia M.; Eppinger, Ben; Schuck, Nicolas W.; Heekeren, Hauke R.; Li, Shu-Chen

2016-01-01

Observational learning is an important mechanism for cognitive and social development. However, the neurophysiological mechanisms underlying observational learning in children are not well understood. In this study, we used a probabilistic reward-based observational learning paradigm to compare behavioral and electrophysiological markers of…

Feeding Behavior Modulates Biofilm-Mediated Transmission of Yersinia pestis by the Cat Flea, Ctenocephalides felis

PubMed Central

Bland, David M.; Hinnebusch, B. Joseph

2016-01-01

Background The cat flea, Ctenocephalides felis, is prevalent worldwide, will parasitize animal reservoirs of plague, and is associated with human habitations in known plague foci. Despite its pervasiveness, limited information is available about the cat flea’s competence as a vector for Yersinia pestis. It is generally considered to be a poor vector, based on studies examining early-phase transmission during the first week after infection, but transmission potential by the biofilm-dependent proventricular-blocking mechanism has never been systematically evaluated. In this study, we assessed the vector competence of cat fleas by both mechanisms. Because the feeding behavior of cat fleas differs markedly from important rat flea vectors, we also examined the influence of feeding behavior on transmission dynamics. Methodology/Principal Findings Groups of cat fleas were infected with Y. pestis and subsequently provided access to sterile blood meals twice-weekly, 5 times per week, or daily for 4 weeks and monitored for infection, the development of proventricular biofilm and blockage, mortality, and the ability to transmit. In cat fleas allowed prolonged, daily access to blood meals, mimicking their natural feeding behavior, Y. pestis did not efficiently colonize the digestive tract and could only be transmitted during the first week after infection. In contrast, cat fleas that were fed intermittently, mimicking the feeding behavior of the efficient vector Xenopsylla cheopis, could become blocked and regularly transmitted Y. pestis for 3–4 weeks by the biofilm-mediated mechanism, but early-phase transmission was not detected. Conclusions The normal feeding behavior of C. felis, more than an intrinsic resistance to infection or blockage by Y. pestis, limits its vector competence. Rapid turnover of midgut contents results in bacterial clearance and disruption of biofilm accumulation in the proventriculus. Anatomical features of the cat flea foregut may also restrict transmission by both early-phase and proventricular biofilm-dependent mechanisms. PMID:26829486

Feeding Behavior Modulates Biofilm-Mediated Transmission of Yersinia pestis by the Cat Flea, Ctenocephalides felis.

PubMed

Bland, David M; Hinnebusch, B Joseph

2016-02-01

The cat flea, Ctenocephalides felis, is prevalent worldwide, will parasitize animal reservoirs of plague, and is associated with human habitations in known plague foci. Despite its pervasiveness, limited information is available about the cat flea's competence as a vector for Yersinia pestis. It is generally considered to be a poor vector, based on studies examining early-phase transmission during the first week after infection, but transmission potential by the biofilm-dependent proventricular-blocking mechanism has never been systematically evaluated. In this study, we assessed the vector competence of cat fleas by both mechanisms. Because the feeding behavior of cat fleas differs markedly from important rat flea vectors, we also examined the influence of feeding behavior on transmission dynamics. Groups of cat fleas were infected with Y. pestis and subsequently provided access to sterile blood meals twice-weekly, 5 times per week, or daily for 4 weeks and monitored for infection, the development of proventricular biofilm and blockage, mortality, and the ability to transmit. In cat fleas allowed prolonged, daily access to blood meals, mimicking their natural feeding behavior, Y. pestis did not efficiently colonize the digestive tract and could only be transmitted during the first week after infection. In contrast, cat fleas that were fed intermittently, mimicking the feeding behavior of the efficient vector Xenopsylla cheopis, could become blocked and regularly transmitted Y. pestis for 3-4 weeks by the biofilm-mediated mechanism, but early-phase transmission was not detected. The normal feeding behavior of C. felis, more than an intrinsic resistance to infection or blockage by Y. pestis, limits its vector competence. Rapid turnover of midgut contents results in bacterial clearance and disruption of biofilm accumulation in the proventriculus. Anatomical features of the cat flea foregut may also restrict transmission by both early-phase and proventricular biofilm-dependent mechanisms.

Unit mechanisms of fission gas release: Current understanding and future needs

DOE PAGES

Tonks, Michael; Andersson, David; Devanathan, Ram; ...

2018-03-01

Gaseous fission product transport and release has a large impact on fuel performance, degrading fuel and gap properties. While gaseous fission product behavior has been investigated with bulk reactor experiments and simplified analytical models, recent improvements in experimental and modeling approaches at the atomistic and mesoscales are beginning to reveal new understanding of the unit mechanisms that define fission product behavior. Here, existing research on the basic mechanisms of fission gas release during normal reactor operation are summarized and critical areas where work is needed are identified. Here, this basic understanding of the fission gas behavior mechanisms has the potentialmore » to revolutionize our ability to predict fission product behavior and to design fuels with improved performance. In addition, this work can serve as a model on how a coupled experimental and modeling approach can be applied to understand the unit mechanisms behind other critical behaviors in reactor materials.« less

Unit mechanisms of fission gas release: Current understanding and future needs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tonks, Michael; Andersson, David; Devanathan, Ram

Gaseous fission product transport and release has a large impact on fuel performance, degrading fuel and gap properties. While gaseous fission product behavior has been investigated with bulk reactor experiments and simplified analytical models, recent improvements in experimental and modeling approaches at the atomistic and mesoscales are beginning to reveal new understanding of the unit mechanisms that define fission product behavior. Here, existing research on the basic mechanisms of fission gas release during normal reactor operation are summarized and critical areas where work is needed are identified. Here, this basic understanding of the fission gas behavior mechanisms has the potentialmore » to revolutionize our ability to predict fission product behavior and to design fuels with improved performance. In addition, this work can serve as a model on how a coupled experimental and modeling approach can be applied to understand the unit mechanisms behind other critical behaviors in reactor materials.« less

Unit mechanisms of fission gas release: Current understanding and future needs

NASA Astrophysics Data System (ADS)

Tonks, Michael; Andersson, David; Devanathan, Ram; Dubourg, Roland; El-Azab, Anter; Freyss, Michel; Iglesias, Fernando; Kulacsy, Katalin; Pastore, Giovanni; Phillpot, Simon R.; Welland, Michael

2018-06-01

Gaseous fission product transport and release has a large impact on fuel performance, degrading fuel and gap properties. While gaseous fission product behavior has been investigated with bulk reactor experiments and simplified analytical models, recent improvements in experimental and modeling approaches at the atomistic and mesoscales are beginning to reveal new understanding of the unit mechanisms that define fission product behavior. Here, existing research on the basic mechanisms of fission gas release during normal reactor operation are summarized and critical areas where work is needed are identified. This basic understanding of the fission gas behavior mechanisms has the potential to revolutionize our ability to predict fission product behavior and to design fuels with improved performance. In addition, this work can serve as a model on how a coupled experimental and modeling approach can be applied to understand the unit mechanisms behind other critical behaviors in reactor materials.

The effects of glycosaminoglycan degradation on the mechanical behavior of the posterior porcine sclera

PubMed Central

Murienne, Barbara J.; Jefferys, Joan L.; Quigley, Harry A.; Nguyen, Thao D.

2014-01-01

Pathological changes in scleral glycosaminoglycan (GAG) content and in scleral mechanical properties have been observed in eyes with glaucoma and myopia. The purpose of this study is to investigate the effect of GAG removal on the scleral mechanical properties to better understand the impact of GAG content variations in the pathophysiology of glaucoma and myopia. We measured how the removal of sulphated GAG (s-GAG) affected the hydration, thickness and mechanical properties of the posterior sclera in enucleated eyes of 6–9 month-old pigs. Measurements were made in 4 regions centered on the optic nerve head (ONH) and evaluated under 3 conditions: no treatment (control), after treatment in buffer solution alone, and after treatment in buffer containing chondroitinase ABC (ChABC) to remove s-GAGs. The specimens were mechanically tested by pressure-controlled inflation with full-field deformation mapping using digital image correlation (DIC). The mechanical outcomes described the tissue tensile and viscoelastic behavior. Treatment with buffer alone increased the hydration of the posterior sclera compared to controls, while s-GAG removal caused a further increase in hydration compared to buffer-treated scleras. Buffer-treatment significantly changed the scleral mechanical behavior compared to the control condition, in a manner consistent with an increase in hydration. Specifically, buffer-treatment led to an increase in low-pressure stiffness, hysteresis, and creep rate, and a decrease in high-pressure stiffness. ChABC-treatment on buffer-treated scleras had opposite mechanical effects than buffer-treatment on controls, leading to a decrease in low-pressure stiffness, hysteresis, and creep rate, and an increase in high-pressure stiffness and transition strain. Furthermore, s-GAG digestion dramatically reduced the differences in the mechanical behavior among the 4 quadrants surrounding the ONH as well as the differences between the circumferential and meridional responses compared to the buffer-treated condition. These findings demonstrate a significant effect of s-GAGs on both the stiffness and time-dependent behavior of the sclera. Alterations in s-GAG content may contribute to the altered creep and stiffness of the sclera of myopic and glaucoma eyes. PMID:25448352

Contact stiffness and damping of liquid films in dynamic atomic force microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Rong-Guang; Leng, Yongsheng, E-mail: leng@gwu.edu

2016-04-21

The mechanical properties and dissipation behaviors of nanometers confined liquid films have been long-standing interests in surface force measurements. The correlation between the contact stiffness and damping of the nanoconfined film is still not well understood. We establish a novel computational framework through molecular dynamics (MD) simulation for the first time to study small-amplitude dynamic atomic force microscopy (dynamic AFM) in a simple nonpolar liquid. Through introducing a tip driven dynamics to mimic the mechanical oscillations of the dynamic AFM tip-cantilever assembly, we find that the contact stiffness and damping of the confined film exhibit distinct oscillations within 6-7 monolayermore » distances, and they are generally out-of-phase. For the solid-like film with integer monolayer thickness, further compression of the film before layering transition leads to higher stiffness and lower damping, while much lower stiffness and higher damping occur at non-integer monolayer distances. These two alternating mechanisms dominate the mechanical properties and dissipation behaviors of simple liquid films under cyclic elastic compression and inelastic squeeze-out. Our MD simulations provide a direct picture of correlations between the structural property, mechanical stiffness, and dissipation behavior of the nanoconfined film.« less

An experimental study of mechanical behavior of natural fiber reinforced polymer matrix composites

NASA Astrophysics Data System (ADS)

Ratna, Sanatan; Misra, Sheelam

2018-05-01

Fibre-reinforced polymer composites have played a dominant role for a long time in a variety of applications for their high specific strength and modulus. The fibre which serves as a reinforcement in reinforced plastics may be synthetic or natural. Past studies show that only synthetic fibres such as glass, carbon etc., have been used in fibre reinforced plastics. Although glass and other synthetic fibre-reinforced plastics possess high specific strength, their fields of application are very limited because of their inherent higher cost of production. In this connection, an investigation has been carried out to make use of horse hair, an animal fibre abundantly available in India. Animal fibres are not only strong and lightweight but also relatively very cheaper than mineral fibre. The present work describes the development and characterization of a new set of animal fiber based polymer composites consisting of horse hair as reinforcement and epoxy resin. The newly developed composites are characterized with respect to their mechanical characteristics. Experiments are carried out to study the effect of fibre length on mechanical behavior of these epoxy based polymer composites. Composite made form horse hair can be used as a potential reinforcing material for many structural and non-structural applications. This work can be further extended to study other aspects of such composites like effect of fiber content, loading pattern, fibre treatment on mechanical behavior of horse hair based polymer horse hair.

Stimulus Fading and Transfer in the Treatment of Self-Restraint and Self-Injurious Behavior.

ERIC Educational Resources Information Center

Pace, Gary M.; And Others

1986-01-01

Manipulation of mechanical restraint properties were conducted in separate studies with two profoundly retarded adolescents who exhibited both self-restraint and self-injurious behavior. Techniques included prompting, differential reinforcement, and stimulus fading. Results suggested that stimulus fading and transfer may be valuable components in…

Neuroscience and morality.

PubMed

Allison, T

2001-10-01

Humans are social animals who use specialized brain mechanisms to assess the actions of others. This system for social cognition can be studied by imaging techniques, and its damage can lead to inappropriate social and moral behavior. Neuroscience can thus enrich our understanding of behaviors traditionally thought to be outside the province of science.

Behavioral and chemical mechanisms of plant-mediated deterrence and attraction among frugivorous insects

USDA-ARS?s Scientific Manuscript database

A number of studies have now reported increased levels of non Bt-targeted secondary pests in Bt crops. Although pesticide reduction plays a role, interactions between the secondary pests and the targeted primary pest may also be important. Feeding preference—attractiveness (selection behavior, acce...

Predicting Adolescent and Adult Antisocial Behavior among Adjudicated Delinquent Females

ERIC Educational Resources Information Center

Cernkovich, Stephen A.; Lanctot, Nadine; Giordano, Peggy C.

2008-01-01

Studies identifying the mechanisms underlying the causes and consequences of antisocial behavior among female delinquents as they transit to adulthood are scarce and have important limitations: Most are based on official statistics, they typically are restricted to normative samples, and rarely do they gather prospective data from samples of…

Preschoolers Use Social Allegiances to Predict Behavior

ERIC Educational Resources Information Center

Chalik, Lisa; Rhodes, Marjorie

2014-01-01

Developing mechanisms for predicting human action is a critical task of early conceptual development. Three studies examined whether 4-year-old children (N = 149) use social allegiances to predict behavior, by testing whether they expect the experiences of social partners to influence individual action. After being exposed to a conflict between…

How did prefire treatments affect the Biscuit Fire?

Treesearch

Crystal Raymond; David L. Peterson

2005-01-01

Most scientific literature supports forest thinning to reduce the severity of wildland fires, but the effectiveness of thinning in modifying fire behavior has not been well documented. The Biscuit Fire of 2002 offered a great opportunity to study the effects of mechanical thinning on fire behavior during a megafire.

Problem-Solving Style, Teaching Style, and Teaching Practices among In-Service Teachers

ERIC Educational Resources Information Center

Mandelbaum, Matthew Gary

2013-01-01

While educational psychologists have found evidence for effective teaching behaviors that lead to academic achievement, pedagogy still lacks prescriptive accuracy for all students at all times. Teaching style and problem-solving style may be underlying mechanisms behind teaching behaviors. The present study looked at these three…

Managerial Attention Patterns: A Micro-Behavioral Analysis.

ERIC Educational Resources Information Center

Sproull, Lee S.

This paper describes a study of managerial behavior in educational organizations that focused on managerial attention as an organizational coupling mechanism. Structured observation was used to collect minute-by-minute time allocation protocols for five first-line education program managers over 20 working days, and these protocols were analyzed…

Parental Depression and Child Behavior Problems: A Pilot Study Examining Pathways of Influence

ERIC Educational Resources Information Center

Xu, Yangmu; Neece, Cameron L.; Parker, Kathleen H.

2014-01-01

Parents of children with autism spectrum disorders (ASD) have higher rates of depressive symptoms than parents of typically developing children and parents of children with other developmental disorders. Parental depressive symptoms are strongly associated with problem behaviors in children; however, the mechanisms through which parental…

Effect of fiber distribution and realignment on the nonlinear and inhomogeneous mechanical properties of human supraspinatus tendon under longitudinal tensile loading.

PubMed

Lake, Spencer P; Miller, Kristin S; Elliott, Dawn M; Soslowsky, Louis J

2009-12-01

Tendon exhibits nonlinear stress-strain behavior that may be partly due to movement of collagen fibers through the extracellular matrix. While a few techniques have been developed to evaluate the fiber architecture of other soft tissues, the organizational behavior of tendon under load has not been determined. The supraspinatus tendon (SST) of the rotator cuff is of particular interest for investigation due to its complex mechanical environment and corresponding inhomogeneity. In addition, SST injury occurs frequently with limited success in treatment strategies, illustrating the need for a better understanding of SST properties. Therefore, the objective of this study was to quantitatively evaluate the inhomogeneous tensile mechanical properties, fiber organization, and fiber realignment under load of human SST utilizing a novel polarized light technique. Fiber distributions were found to become more aligned under load, particularly during the low stiffness toe-region, suggesting that fiber realignment may be partly responsible for observed nonlinear behavior. Fiber alignment was found to correlate significantly with mechanical parameters, providing evidence for strong structure-function relationships in tendon. Human SST exhibits complex, inhomogeneous mechanical properties and fiber distributions, perhaps due to its complex loading environment. Surprisingly, histological grade of degeneration did not correlate with mechanical properties.

Obedience and motivation as mechanisms for adherence to medication: a study in obese type 2 diabetic patients

PubMed Central

Reach, Gérard

2011-01-01

Objective To clarify the mechanisms of adherence. Methods A cross-sectional, multicenter French study using a self-questionnaire administered by 116 general practitioners to 782 obese type 2 diabetic patients. Results The analysis of 670 completed questionnaires revealed a strong association between the adherence to medication and the behavior of fastening the seatbelt when seated in the rear of a car. Multivariate analysis indicated that this behavior was an independent determinant of adherence to medication (odds ratio [OR] 2.3, 95% confidence interval [CI] 1.4–3.6, P < 0.001) with the same OR as the motivation to adhere to medical prescriptions (OR 2.2, 95% CI 1.3–3.6, P = 0.003) in a model with good accuracy (area under the receiver operating characteristic curve 0.774). A multiple correspondence analysis suggested that adherence to medication and seatbelt behavior are “homologous” behaviors, with homology between phenomena defined by the fact that they share a common etiology. Conclusion Adherence may have two dimensions: passive (obedience, the main determinant of seatbelt behavior) and active (motivation). This conclusion has theoretical and practical implications. Firstly, empowerment through patient education can be defined as a process that replaces the passive mechanism of adherence in patients’ minds with an active, conscious choice. Secondly, recognizing these two dimensions may help to establish a tailored patient-physician relationship to prevent nonadherence. PMID:22114466

Thermo-mechanical behavior and structure of melt blown shape-memory polyurethane nonwovens.

PubMed

Safranski, David L; Boothby, Jennifer M; Kelly, Cambre N; Beatty, Kyle; Lakhera, Nishant; Frick, Carl P; Lin, Angela; Guldberg, Robert E; Griffis, Jack C

2016-09-01

New processing methods for shape-memory polymers allow for tailoring material properties for numerous applications. Shape-memory nonwovens have been previously electrospun, but melt blow processing has yet to be evaluated. In order to determine the process parameters affecting shape-memory behavior, this study examined the effect of air pressure and collector speed on the mechanical behavior and shape-recovery of shape-memory polyurethane nonwovens. Mechanical behavior was measured by dynamic mechanical analysis and tensile testing, and shape-recovery was measured by unconstrained and constrained recovery. Microstructure changes throughout the shape-memory cycle were also investigated by micro-computed tomography. It was found that increasing collector speed increases elastic modulus, ultimate strength and recovery stress of the nonwoven, but collector speed does not affect the failure strain or unconstrained recovery. Increasing air pressure decreases the failure strain and increases rubbery modulus and unconstrained recovery, but air pressure does not influence recovery stress. It was also found that during the shape-memory cycle, the connectivity density of the fibers upon recovery does not fully return to the initial values, accounting for the incomplete shape-recovery seen in shape-memory nonwovens. With these parameter to property relationships identified, shape-memory nonwovens can be more easily manufactured and tailored for specific applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Simulation of the mechanical behavior of random fiber networks with different microstructure.

PubMed

Hatami-Marbini, H

2018-05-24

Filamentous protein networks are broadly encountered in biological systems such as cytoskeleton and extracellular matrix. Many numerical studies have been conducted to better understand the fundamental mechanisms behind the striking mechanical properties of these networks. In most of these previous numerical models, the Mikado algorithm has been used to represent the network microstructure. Here, a different algorithm is used to create random fiber networks in order to investigate possible roles of architecture on the elastic behavior of filamentous networks. In particular, random fibrous structures are generated from the growth of individual fibers from random nucleation points. We use computer simulations to determine the mechanical behavior of these networks in terms of their model parameters. The findings are presented and discussed along with the response of Mikado fiber networks. We demonstrate that these alternative networks and Mikado networks show a qualitatively similar response. Nevertheless, the overall elasticity of Mikado networks is stiffer compared to that of the networks created using the alternative algorithm. We describe the effective elasticity of both network types as a function of their line density and of the material properties of the filaments. We also characterize the ratio of bending and axial energy and discuss the behavior of these networks in terms of their fiber density distribution and coordination number.

Effects of extrusion and heat treatment on the mechanical properties and biocorrosion behaviors of a Mg-Nd-Zn-Zr alloy.

PubMed

Zhang, Xiaobo; Yuan, Guangyin; Mao, Lin; Niu, Jialin; Fu, Penghuai; Ding, Wenjiang

2012-03-01

Mechanical properties at room temperature and biocorrosion behaviors in simulated body fluid (SBF) at 37 °C of a new type of patented Mg-3Nd-0.2Zn-0.4Zr (hereafter, denoted as JDBM) alloy prepared at different extrusion temperatures, as well as heat treatment, were studied. The mechanical properties of this magnesium alloy at room temperature were improved significantly after extrusion and heat treatment compared to an as-cast alloy. The results of mechanical properties show that the yield strength (YS) decreases with increasing extrusion temperature. The tensile elongation decreases a little while the ultimate tensile strength (UTS) has no obvious difference. The yield strength and ultimate tensile strength were improved clearly after heat treatment at 200 °C for 10 h compared with that at the extrusion state, which can be mainly contributed to the precipitation strengthening. The biocorrosion behaviors of the JDBM alloy were studied using immersion tests and electrochemical tests. The results reveal that the extruded JDBM alloy and the aging treatment on the extruded alloy show much better biocorrosion resistance than that at solid solution state (T4 treatment), and the JDBM exhibited favorable uniform corrosion mode in SBF. Copyright © 2011 Elsevier Ltd. All rights reserved.

Traumatic Brain Injury – Modeling Neuropsychiatric Symptoms in Rodents

PubMed Central

Malkesman, Oz; Tucker, Laura B.; Ozl, Jessica; McCabe, Joseph T.

2013-01-01

Each year in the US, ∼1.5 million people sustain a traumatic brain injury (TBI). Victims of TBI can suffer from chronic post-TBI symptoms, such as sensory and motor deficits, cognitive impairments including problems with memory, learning, and attention, and neuropsychiatric symptoms such as depression, anxiety, irritability, aggression, and suicidal rumination. Although partially associated with the site and severity of injury, the biological mechanisms associated with many of these symptoms – and why some patients experience differing assortments of persistent maladies – are largely unknown. The use of animal models is a promising strategy for elucidation of the mechanisms of impairment and treatment, and learning, memory, sensory, and motor tests have widespread utility in rodent models of TBI and psychopharmacology. Comparatively, behavioral tests for the evaluation of neuropsychiatric symptomatology are rarely employed in animal models of TBI and, as determined in this review, the results have been inconsistent. Animal behavioral studies contribute to the understanding of the biological mechanisms by which TBI is associated with neurobehavioral symptoms and offer a powerful means for pre-clinical treatment validation. Therefore, further exploration of the utility of animal behavioral tests for the study of injury mechanisms and therapeutic strategies for the alleviation of emotional symptoms are relevant and essential. PMID:24109476

A multi-scale and multi-field coupling nonlinear constitutive theory for the layered magnetoelectric composites

NASA Astrophysics Data System (ADS)

Xu, Hao; Pei, Yongmao; Li, Faxin; Fang, Daining

2018-05-01

The magnetic, electric and mechanical behaviors are strongly coupled in magnetoelectric (ME) materials, making them great promising in the application of functional devices. In this paper, the magneto-electro-mechanical fully coupled constitutive behaviors of ME laminates are systematically studied both theoretically and experimentally. A new probabilistic domain switching function considering the surface ferromagnetic anisotropy and the interface charge-mediated effect is proposed. Then a multi-scale multi-field coupling nonlinear constitutive model for layered ME composites is developed with physical measureable parameters. The experiments were performed to compare the theoretical predictions with the experimental data. The theoretical predictions have a good agreement with experimental results. The proposed constitutive relation can be used to describe the nonlinear multi-field coupling properties of both ME laminates and thin films. Several novel coupling experimental phenomena such as the electric-field control of magnetization, and the magnetic-field tuning of polarization are observed and analyzed. Furthermore, the size-effect of the electric tuning behavior of magnetization is predicted, which demonstrates a competition mechanism between the interface strain-mediated effect and the charge-driven effect. Our study offers deep insight into the coupling microscopic mechanism and macroscopic properties of ME layered composites, which is benefit for the design of electromagnetic functional devices.

Sensitive periods in epigenetics: bringing us closer to complex behavioral phenotypes.

PubMed

Nagy, Corina; Turecki, Gustavo

2012-08-01

Genetic studies have attempted to elucidate causal mechanisms for the development of complex disease, but genome-wide associations have been largely unsuccessful in establishing these links. As an alternative link between genes and disease, recent efforts have focused on mechanisms that alter the function of genes without altering the underlying DNA sequence. Known as epigenetic mechanisms, these include DNA methylation, chromatin conformational changes through histone modifications, ncRNAs and, most recently, 5-hydroxymethylcytosine. Although DNA methylation is involved in normal development, aging and gene regulation, altered methylation patterns have been associated with disease. It is generally believed that early life constitutes a period during which there is increased sensitivity to the regulatory effects of epigenetic mechanisms. The purpose of this review is to outline the contribution of epigenetic mechanisms to genomic function, particularly in the development of complex behavioral phenotypes, focusing on the sensitive periods.

Sensitive Periods in Epigenetics: bringing us closer to complex behavioral phenotypes

PubMed Central

Nagy, Corina; Turecki, Gustavo

2017-01-01

Genetic studies have attempted to elucidate causal mechanisms for the development of complex disease but genome-wide associations have been largely unsuccessful in establishing these links. As an alternative link between genes and disease, recent efforts have focused on mechanisms that alter the function of genes without altering the underlying DNA sequence. Known as epigenetic mechanisms, these include: DNA methylation, chromatin conformational changes through histone modifications, non-coding RNAs, and most recently, 5-hydroxymethylcytosine. Though DNA methylation is involved in normal development, aging and gene regulation, altered methylation patterns have been associated with disease. It is generally believed that early life constitutes a period during which there is increased sensitivity to the regulatory effects of epigenetic mechanisms. The purpose of this review is to outline the contribution of epigenetic mechanisms to genomic function, particularly in the development of complex behavioral phenotypes, focusing on the sensitive periods. PMID:22920183

Structural, Kinetic And Magnetic Properties Of Mechanically Alloyed Fe-Zr Powders

NASA Astrophysics Data System (ADS)

Mishra, Debabrata; Perumal, A.; Srinivasan, A.

2008-04-01

We report the study of amorphous/non-equilibrium solid solution Fe100-xZrx (x = 20 to 35) alloys by mechanical alloying process. It is observed that with increasing Zr substitution, (a) the activation energy increases, (b) the saturation magnetization and coercivity show oscillating behavior. Low temperature magnetic measurements show the presence of spin-glass like phase transition even at H = 10 kOe. The oscillating behavior of magnetic parameters is explained on the basis of variations in the average internal stress calculated using magnetic data.

A three-dimensional collagen-fiber network model of the extracellular matrix for the simulation of the mechanical behaviors and micro structures.

PubMed

Dong, Shoubin; Huang, Zetao; Tang, Liqun; Zhang, Xiaoyang; Zhang, Yongrou; Jiang, Yi

2017-07-01

The extracellular matrix (ECM) provides structural and biochemical support to cells and tissues, which is a critical factor for modulating cell dynamic behavior and intercellular communication. In order to further understand the mechanisms of the interactive relationship between cell and the ECM, we developed a three-dimensional (3D) collagen-fiber network model to simulate the micro structure and mechanical behaviors of the ECM and studied the stress-strain relationship as well as the deformation of the ECM under tension. In the model, the collagen-fiber network consists of abundant random distributed collagen fibers and some crosslinks, in which each fiber is modeled as an elastic beam and a crosslink is modeled as a linear spring with tensile limit, it means crosslinks will fail while the tensile forces exceed the limit of spring. With the given parameters of the beam and the spring, the simulated tensile stress-strain relation of the ECM highly matches the experimental results including damaged and failed behaviors. Moreover, by applying the maximal inscribed sphere method, we measured the size distribution of pores in the fiber network and learned the variation of the distribution with deformation. We also defined the alignment of the collagen-fibers to depict the orientation of fibers in the ECM quantitatively. By the study of changes of the alignment and the damaged crosslinks against the tensile strain, this paper reveals the comprehensive mechanisms of four stages of 'toe', 'linear', 'damage' and 'failure' in the tensile stress-strain relation of the ECM which can provide further insight in the study of cell-ECM interaction.

Co-regulation of female sexual behavior and pregnancy induction: an exploratory synthesis.

PubMed

Erskine, Mary S; Lehmann, Michael L; Cameron, Nicole M; Polston, Eva K

2004-08-31

This paper will review both new and old data that address the question of whether brain mechanisms involved in reproductive function act in a coordinated way to control female sexual behavior and the induction of pregnancy/pseudopregnancy (P/PSP) by vaginocervical stimulation. Although it is clear that female sexual behavior, including pacing behavior, is important for induction of P/PSP, there has been no concerted effort to examine whether or how common mechanisms may control both functions. Because initiation of P/PSP requires that the female receive vaginocervical stimulation, central mechanisms controlling P/PSP may be modulated by or interactive with those that control female sexual behavior. This paper presents a synthesis of the literature and recent data from our lab for the purpose of examining whether there are interactions between behavioral and neuroendocrine mechanisms which reciprocally influence both reproductive functions.

A conceptual model of patient-professional communication as a self-management skill: A latent growth change modeling.

PubMed

Chan, Sam C C; Chan, Chetwyn C H; Siu, Andrew M H; Poon, Peter K K

2015-10-01

Patient Communication with healthcare professionals is an integral self-management skill. Yet the underlying mechanisms explaining how such communication might be enhanced across time have not been well studied. Based on the transtheoretical model, the study aimed to develop an across-time Attitude-Social Influence-Efficacy model in order to explain changes in participants' patient-professional communication behaviors in the Chronic Disease Self-management Program (CDSMP). Readiness-to-change construct was hypothesized to be the overall predictors of psychological and behavioral parameters. It was hypothesized that social norm and attitude toward behaviors would be the indirect predictors of communication behavior. One hundred and thirty-six Chinese participants with chronic diseases underwent a 6-week CDSMP. Their attitude toward behavior, self-efficacy, social norm, readiness to change and communication behavior were obtained at 1st, 4th and 6th week of the structured program. A modified latent growth change curve model yielded satisfactory model fit (χ(2)/df = 1.32; RMSEA = 0.063 (90% CI = 0.018-0.96)). The results showed that readiness to change had a positive influence on attitude and self-efficacy. Both attitude and social norm positively affected self-efficacy. Attitude and self-efficacy in turn positively influenced communication behavior at the beginning of the program. Across 6 weeks, self-efficacy imposed a negative influence on communication behavior while social norm exerted a positive influence on the behavior. This study revealed possible underlying mechanisms influencing CDSMP participants' communication with professionals. The results could shed light on further improvement of the structured program. Copyright © 2015 Elsevier Inc. All rights reserved.

Effects of Combat Deployment on Risky and Self-Destructive Behavior Among Active Duty Military Personnel

DTIC Science & Technology

2011-01-01

Research has docu- mented increases in psychological problems among personnel returning from combat deployment. Although most studies have focused on...1995; Hoge et al., 2004). Compar- atively less attention has been paid to potential effects of deploy- ment on other psychological and behavioral health...Zuckerman, 2007). There are several mechanisms by which combat deployment might increase risky behavior. Joiner’s (2005) interpersonal- psychological

Comparison of Crack Initiation, Propagation and Coalescence Behavior of Concrete and Rock Materials

NASA Astrophysics Data System (ADS)

Zengin, Enes; Abiddin Erguler, Zeynal

2017-04-01

There are many previously studies carried out to identify crack initiation, propagation and coalescence behavior of different type of rocks. Most of these studies aimed to understand and predict the probable instabilities on different engineering structures such as mining galleries or tunnels. For this purpose, in these studies relatively smaller natural rock and synthetic rock-like models were prepared and then the required laboratory tests were performed to obtain their strength parameters. By using results provided from these models, researchers predicted the rock mass behavior under different conditions. However, in the most of these studies, rock materials and models were considered as contains none or very few discontinuities and structural flaws. It is well known that rock masses naturally are extremely complex with respect to their discontinuities conditions and thus it is sometimes very difficult to understand and model their physical and mechanical behavior. In addition, some vuggy rock materials such as basalts and limestones also contain voids and gaps having various geometric properties. Providing that the failure behavior of these type of rocks controlled by the crack initiation, propagation and coalescence formed from their natural voids and gaps, the effect of these voids and gaps over failure behavior of rocks should be investigated. Intact rocks are generally preferred due to relatively easy side of their homogeneous characteristics in numerical modelling phases. However, it is very hard to extract intact samples from vuggy rocks because of their complex pore sizes and distributions. In this study, the feasibility of concrete samples to model and mimic the failure behavior vuggy rocks was investigated. For this purpose, concrete samples were prepared at a mixture of %65 cement dust and %35 water and their physical and mechanical properties were determined by laboratory experiments. The obtained physical and mechanical properties were used to constitute numerical models, and then uniaxial compressive strength (UCS) tests were performed on these models by using a commercial software called as Particle Flow Code (PFC2D). When the crack behavior of concrete samples obtained from both laboratory tests and numerical models are compared with the results of previous studies, a significant similarity was found. As a result, due to the observed similarity crack behavior between concretes and rocks, it can be concluded that intact concrete samples can be used for modelling purposes to understand the effect of voids and gaps on failure characteristics of vuggy rocks.

Social visual engagement in infants and toddlers with autism: Early developmental transitions and a model of pathogenesis

PubMed Central

Klin, Ami; Shultz, Sarah; Jones, Warren

2014-01-01

Efforts to determine and understand the causes of autism are currently hampered by a large disconnect between recent molecular genetics findings that are associated with the condition and the core behavioral symptoms that define the condition. In this perspective piece, we propose a systems biology framework to bridge that gap between genes and symptoms. The framework focuses on basic mechanisms of socialization that are highly-conserved in evolution and are early-emerging in development. By conceiving of these basic mechanisms of socialization as quantitative endophenotypes, we hope to connect genes and behavior in autism through integrative studies of neurodevelopmental, behavioral, and epigenetic changes. These changes both lead to and are led by the accomplishment of specific social adaptive tasks in a typical infant's life. However, based on recent research that indicates that infants later diagnosed with autism fail to accomplish at least some of these tasks, we suggest that a narrow developmental period, spanning critical transitions from reflexive, subcortically-controlled visual behavior to interactional, cortically-controlled and social visual behavior be prioritized for future study. Mapping epigenetic, neural, and behavioral changes that both drive and are driven by these early transitions may shed a bright light on the pathogenesis of autism. PMID:25445180

Dialectical Behavior Therapy Skills Use as a Mediator and Outcome of Treatment for Borderline Personality Disorder

PubMed Central

Neacsiu, Andrada D.; Rizvi, Shireen L.; Linehan, Marsha M.

2010-01-01

A central component of Dialectical Behavior Therapy (DBT) is the teaching of specific behavioral skills with the aim of helping individuals with Borderline Personality Disorder (BPD) replace maladaptive behaviors with skillful behavior. Although existing evidence indirectly supports this proposed mechanism of action, no study to date has directly tested it. Therefore, we examined the skills use of 108 women with BPD participating in one of three randomized control trials throughout one year of treatment and four months of follow-up. Using a hierarchical linear modeling approach we found that although all participants reported using some DBT skills before treatment started, participants treated with DBT reported using three times more skills at the end of treatment than participants treated with a control treatment. Significant mediation effects also indicated that DBT skills use fully mediated the decrease in suicide attempts and depression and the increase in control of anger over time. DBT skills use also partially mediated the decrease of nonsuicidal self-injury over time. Anger suppression and expression were not mediated. This study is the first to clearly support the skills deficit model for BPD by indicating that increasing skills use is a mechanism of change for suicidal behavior, depression, and anger control. PMID:20579633

[Possible evolutionary mechanisms of 'culture' in animals: The hypothesis of distributed social learning].

PubMed

Reznikova, Zh I; Panteleeva, S N

2015-01-01

There is a plethora of works on the origin and genesis of behavioral traditions in different animal species. Nevertheless, it still remains unclear as for which factors facilitate and which factors hinder the spreading those forms of behavior that are new for a population. Here, we present an analytical review on the topic, considering also the results of studies on 'culture' in animals and analyzing contradictions that arise when attempting to clarify the ethological mechanisms of cultural succession. The hypothesis of 'distributed social learning' is formulated, meaning that for spreading of complex behavioral stereotypes in a population the presence of few carriers of consistent stereotypes is enough under the condition that the rest of animals carry incomplete genetic programmes that start up these stereotypes. Existence of 'dormant' fragments of such programmes determines an inborn predisposition of their bearer to perform a certain sequence of acts. To complete the consistent stereotype, the simplest forms of social learning ('social alleviation') turn to be enough. The hypothesis is examined at the behavioral level and supported by experimental data obtained when studying the scenarios of hunting behavior development in ants Myrmica rubra L. It makes possible to explain the spreading of behavioral models in animal communities in a simpler way than cultural succession.

Are Empowered Employees More Proactive? The Contingency of How They Evaluate Their Leader

PubMed Central

Yin, Kui; Xing, Lu; Li, Can; Guo, Yungui

2017-01-01

Finding ways to enhance employee proactive behavior is a focal concern for academics and practitioners. Previous studies have found a positive association between empowering leadership and proactive behavior (Martin et al., 2013; Li et al., 2017). However, these studies lack elaboration on mechanisms and do not rule out the effect of employees’ proactive personality during empirical testing. We investigate empowering leadership from individual perspective due to the variation of empowerment levels even in the same team. Our research proposes a more elaborated theoretical model that explains why, and when, empowering leadership might promote employee proactive behavior. Specifically, we examine mediating mechanisms based on social cognitive theory and propose trust in leader competency as boundary condition. Using a sample of 280 leader–follower dyads from a large state-owned Chinese company, our results revealed that (1) empowering leadership was positively related to proactive behavior, with role breadth self-efficacy acting as a mediator for this relationship; (2) employees’ trust in leader competency moderated both the empowering leadership–subordinate proactive behavior relationship and the mediating effect of role breadth self-efficacy, such that the empowering leadership–subordinate proactive behavior relationship was weaker, and the mediating effect of role breadth self-efficacy was stronger, for employees with high levels of trust in leader competency. PMID:29163249

Are Empowered Employees More Proactive? The Contingency of How They Evaluate Their Leader.

PubMed

Yin, Kui; Xing, Lu; Li, Can; Guo, Yungui

2017-01-01

Finding ways to enhance employee proactive behavior is a focal concern for academics and practitioners. Previous studies have found a positive association between empowering leadership and proactive behavior (Martin et al., 2013; Li et al., 2017). However, these studies lack elaboration on mechanisms and do not rule out the effect of employees' proactive personality during empirical testing. We investigate empowering leadership from individual perspective due to the variation of empowerment levels even in the same team. Our research proposes a more elaborated theoretical model that explains why, and when, empowering leadership might promote employee proactive behavior. Specifically, we examine mediating mechanisms based on social cognitive theory and propose trust in leader competency as boundary condition. Using a sample of 280 leader-follower dyads from a large state-owned Chinese company, our results revealed that (1) empowering leadership was positively related to proactive behavior, with role breadth self-efficacy acting as a mediator for this relationship; (2) employees' trust in leader competency moderated both the empowering leadership-subordinate proactive behavior relationship and the mediating effect of role breadth self-efficacy, such that the empowering leadership-subordinate proactive behavior relationship was weaker, and the mediating effect of role breadth self-efficacy was stronger, for employees with high levels of trust in leader competency.

Social visual engagement in infants and toddlers with autism: early developmental transitions and a model of pathogenesis.

PubMed

Klin, Ami; Shultz, Sarah; Jones, Warren

2015-03-01

Efforts to determine and understand the causes of autism are currently hampered by a large disconnect between recent molecular genetics findings that are associated with the condition and the core behavioral symptoms that define the condition. In this perspective piece, we propose a systems biology framework to bridge that gap between genes and symptoms. The framework focuses on basic mechanisms of socialization that are highly-conserved in evolution and are early-emerging in development. By conceiving of these basic mechanisms of socialization as quantitative endophenotypes, we hope to connect genes and behavior in autism through integrative studies of neurodevelopmental, behavioral, and epigenetic changes. These changes both lead to and are led by the accomplishment of specific social adaptive tasks in a typical infant's life. However, based on recent research that indicates that infants later diagnosed with autism fail to accomplish at least some of these tasks, we suggest that a narrow developmental period, spanning critical transitions from reflexive, subcortically-controlled visual behavior to interactional, cortically-controlled and social visual behavior be prioritized for future study. Mapping epigenetic, neural, and behavioral changes that both drive and are driven by these early transitions may shed a bright light on the pathogenesis of autism. Copyright © 2014 Elsevier Ltd. All rights reserved.

Four studies on how past and current suicidality relate even when "everything but the kitchen sink" is covaried.

PubMed

Joiner, Thomas E; Conwell, Yeates; Fitzpatrick, Kathleen Kara; Witte, Tracy K; Schmidt, Norman B; Berlim, Marcelo T; Fleck, Marcelo P A; Rudd, M David

2005-05-01

T. E. Joiner's (2004, in press) theory of suicidal behavior suggests that past suicidal behavior plays an important role in future suicidality. However, the mechanism by which this risk is transferred and the causal implications have not been well studied. The current study provides evaluation of the nature and limits of this relationship across 4 populations, with varying degrees of suicidal behavior. Across settings, age groups, and impairment levels, the association between past suicidal behavior and current suicidal symptoms held, even when controlling for strong covariates like hopelessness and symptoms of various Axis I and II syndromes. Results provide additional support for the importance of past suicidality as a substantive risk factor for later suicidal behavior. Copyright 2005 APA, all rights reserved.

Novel rodent model of breast cancer survival with persistent anxiety-like behavior and inflammation.

PubMed

Pyter, Leah M; Suarez-Kelly, Lorena P; Carson, William E; Kaur, Jasskiran; Bellisario, Joshua; Bever, Savannah R

2017-07-14

Breast cancer survivors are an expanding population that is troubled by lasting mental health problems, including depression and anxiety. These issues reduce quality-of-life throughout survivorhood. Research indicates that tumor biology, cancer treatments, and stress contribute to these mood disturbances. Although the mechanisms underlying these various causes remain under investigation, neuroinflammation is a leading hypothesis. To date, rodent models of recurrence-free tumor survival for understanding mechanisms by which these behavioral issues persist after cancer are lacking. Here, we test the extent to which potential behavioral symptoms persist after mammary tumor removal in mice (i.e., establishment of a cancer survivor model), while also empirically testing the causal role of tumors in the development of neuroinflammatory-mediated affective-like behaviors. Complete surgical resection of a non-metastatic orthotopic, syngeneic mammary tumor reversed tumor-induced increases of circulating cytokines (IL-6, CXCL1, IL-10) and myeloid-derived cells and modulated neuroinflammatory gene expression (Cd11b, Cxcl1). Multiple anxiety-like behaviors and some central and peripheral immune markers persisted or progressed three weeks after tumor resection. Together, these data indicate that persistent behavioral changes into cancer survivorhood may be due, in part, to changes in immunity that remain even after successful tumor removal. This novel survivor paradigm represents an improvement in modeling prevalent cancer survivorship issues and studying the basic mechanisms by which cancer/cancer treatments influence the brain and behavior. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of optical attenuation, heat diffusion, and acoustic coherence in photoacoustic signals produced by nanoparticles

NASA Astrophysics Data System (ADS)

Alba-Rosales, J. E.; Ramos-Ortiz, G.; Escamilla-Herrera, L. F.; Reyes-Ramírez, B.; Polo-Parada, L.; Gutiérrez-Juárez, G.

2018-04-01

The behavior of the photoacoustic signal produced by nanoparticles as a function of their concentration was studied in detail. As the concentration of nanoparticles is increased in a sample, the peak-to-peak photoacoustic amplitude increases linearly up to a certain value, after which an asymptotic saturated behavior is observed. To elucidate the mechanisms responsible for these observations, we evaluate the effects of nanoparticles concentration, the optical attenuation, and the effects of heat propagation from nano-sources to their surroundings. We found that the saturation effect of the photoacoustic signal as a function of the concentration of nanoparticles is explained by a combination of two different mechanisms. As has been suggested previously, but not modeled correctly, the most important mechanism is attributed to optical attenuation. The second mechanism is due to an interference destructive process attributed to the superimposition of the photoacoustic amplitudes generated for each nanoparticle, and this explanation is reinforced through our experimental and simulations results; based on this, it is found that the linear behavior of the photoacoustic amplitude could be restricted to optical densities ≤0.5.

The Dilemmas of the Gourmet Fly: The Molecular and Neuronal Mechanisms of Feeding and Nutrient Decision Making in Drosophila

PubMed Central

Itskov, Pavel M.; Ribeiro, Carlos

2012-01-01

To survive and successfully reproduce animals need to maintain a balanced intake of nutrients and energy. The nervous system of insects has evolved multiple mechanisms to regulate feeding behavior. When animals are faced with the choice to feed, several decisions must be made: whether or not to eat, how much to eat, what to eat, and when to eat. Using Drosophila melanogaster substantial progress has been achieved in understanding the neuronal and molecular mechanisms controlling feeding decisions. These feeding decisions are implemented in the nervous system on multiple levels, from alterations in the sensitivity of peripheral sensory organs to the modulation of memory systems. This review discusses methodologies developed in order to study insect feeding, the effects of neuropeptides and neuromodulators on feeding behavior, behavioral evidence supporting the existence of internal energy sensors, neuronal and molecular mechanisms controlling protein intake, and finally the regulation of feeding by circadian rhythms and sleep. From the discussed data a conceptual framework starts to emerge which aims to explain the molecular and neuronal processes maintaining the stability of the internal milieu. PMID:23407678

Insecticide resistance and resistance mechanisms in bed bugs, Cimex spp. (Hemiptera: Cimicidae).

PubMed

Dang, Kai; Doggett, Stephen L; Veera Singham, G; Lee, Chow-Yang

2017-06-29

The worldwide resurgence of bed bugs [both Cimex lectularius L. and Cimex hemipterus (F.)] over the past two decades is believed in large part to be due to the development of insecticide resistance. The transcriptomic and genomic studies since 2010, as well as morphological, biochemical and behavioral studies, have helped insecticide resistance research on bed bugs. Multiple resistance mechanisms, including penetration resistance through thickening or remodelling of the cuticle, metabolic resistance by increased activities of detoxification enzymes (e.g. cytochrome P450 monooxygenases and esterases), and knockdown resistance by kdr mutations, have been experimentally identified as conferring insecticide resistance in bed bugs. Other candidate resistance mechanisms, including behavioral resistance, some types of physiological resistance (e.g. increasing activities of esterases by point mutations, glutathione S-transferase, target site insensitivity including altered AChEs, GABA receptor insensitivity and altered nAChRs), symbiont-mediated resistance and other potential, yet undiscovered mechanisms may exist. This article reviews recent studies of resistance mechanisms and the genes governing insecticide resistance, potential candidate resistance mechanisms, and methods of monitoring insecticide resistance in bed bugs. This article provides an insight into the knowledge essential for the development of both insecticide resistance management (IRM) and integrated pest management (IPM) strategies for successful bed bug management.

Conservative Diffusions: a Constructive Approach to Nelson's Stochastic Mechanics.

NASA Astrophysics Data System (ADS)

Carlen, Eric Anders

In Nelson's stochastic mechanics, quantum phenomena are described in terms of diffusions instead of wave functions; this thesis is a study of that description. We emphasize that we are concerned here with the possibility of describing, as opposed to explaining, quantum phenomena in terms of diffusions. In this direction, the following questions arise: "Do the diffusions of stochastic mechanics--which are formally given by stochastic differential equations with extremely singular coefficients--really exist?" Given that they exist, one can ask, "Do these diffusions have physically reasonable sample path behavior, and can we use information about sample paths to study the behavior of physical systems?" These are the questions we treat in this thesis. In Chapter I we review stochastic mechanics and diffusion theory, using the Guerra-Morato variational principle to establish the connection with the Schroedinger equation. This chapter is largely expository; however, there are some novel features and proofs. In Chapter II we settle the first of the questions raised above. Using PDE methods, we construct the diffusions of stochastic mechanics. Our result is sufficiently general to be of independent mathematical interest. In Chapter III we treat potential scattering in stochastic mechanics and discuss direct probabilistic methods of studying quantum scattering problems. Our results provide a solid "Yes" in answer to the second question raised above.

High temperature deformation of Vitreloy bulk metallic glasses and their composite

NASA Astrophysics Data System (ADS)

Tao, Min

A complete understanding of the deformation mechanisms of BMGs and their composites requires investigation of the microstructural changes and their interplay with the mechanical behavior. In this dissertation, the deformation mechanisms of a series of Vitreloy glasses and their composites are experimentally investigated over a wide range of strain rates and temperatures, with focus on the supercooled liquid regime, by combining uniaxial mechanical testing with calorimetric and microscopic examinations. Various theories of deformation of metallic glasses and the composites are examined in light of the experimental data. A comparative structural relaxation study was performed on two closely related Vitreloy alloys, Zr41.2Ti13.8Cu12.5Ni 10Be22.5 (Vit 1) and Zr46.7Ti8.3Cu 7.5Ni10Be27.5 (Vit 4). Differential scanning calorimetric studies on the specimens deformed in compression at constant-strain-rate in supercooled liquid regime showed that mechanical loading accelerated the spinodal phase separation and nanocrystallization process in Vit 1, while the relaxation in Vit 4 featured local chemical composition fluctuation accompanied by annealing out of free volume. The effect of the structural relaxation on their mechanical behavior was further studied via single and multiple jump-in-strain-rate tests. The deformation and viscosity of a new Vitreloy alloy were characterized using uniaxial compression tests in its supercooled liquid regime. A new theoretical model named Cooperative Shear Model, which correlates the evolution of the macroscopic mechanical/thermal variables such as shear modulus and viscosity with the configurational energies of atom clusters in an amorphous alloy, was critically examined in this investigation. The model was successful in predicting the Newtonian and non-Newtonian viscosities of the material, as well as the shear moduli of the deformed specimens, in a self-consistent manner. The plastic flow of an in-situ metallic glass composite, beta-Vitreloy, was investigated under uniaxial compression in its supercooled liquid regime and at various strain rates (10-4 ˜ 10-1 s-1). The composite, with ˜ 25% volume fraction of crystalline beta-phase dendrites exhibited superplastic behavior similar to that of amorphous Vit 1. Significant strain hardening was observed when the material was deformed at high temperatures and low strain rates. A dual-phase composite model was employed in finite element simulations to understand the effect of the composite microstructure on its mechanical behavior.

Gambling behavior in Parkinson's Disease: Impulsivity, reward mechanism and cortical brain oscillations.

PubMed

Balconi, Michela; Angioletti, Laura; Siri, Chiara; Meucci, Nicoletta; Pezzoli, Gianni

2018-03-20

Psychopathological components, such as reward sensitivity and impulsivity, and dopaminergic treatment are crucial characteristics related to the development of Pathological Gambling (PG) in Parkinson's Disease (PD). The aim of the present study is to investigate the differences in decision-making in PD patients with or without PG considering both neurophysiological and behavioral aspects. The IOWA Gambling Task (IGT) and electroencephalographic (EEG) activity were considered to elucidate the decision and post-feedback processes in PG. The sample included fifty-two PD patients, divided in three groups: 17 PD patients with active gambling behavior (PD Gamblers, PDG); 15 PD patients who remitted from PG (PD Non-Gamblers, PDNG); and a Control Group (CG) composed by 20 patients with PD only. EEG and IGT performance were recorded during decision and post-feedback phase. Results showed worse performance and an increase of the low frequency bands in the frontal area for the PDG group compared to the other two groups. In addition, higher BAS (Behavioral Activation System) and BIS-11 (Barratt Impulsiveness Scale) personality components were correlated to groups' behavioral response. These results show an anomalous behavioral (IGT) and cortical response of PDG patients related to their inability to use adequate control mechanisms during a decision-making task where reward mechanisms (BAS) and impulsivity (BIS-11) are relevant. Copyright © 2018 Elsevier B.V. All rights reserved.

Impacts of relative permeability on CO2 phase behavior, phase distribution, and trapping mechanisms

NASA Astrophysics Data System (ADS)

Moodie, N.; McPherson, B. J. O. L.; Pan, F.

2015-12-01

A critical aspect of geologic carbon storage, a carbon-emissions reduction method under extensive review and testing, is effective multiphase CO2 flow and transport simulation. Relative permeability is a flow parameter particularly critical for accurate forecasting of multiphase behavior of CO2 in the subsurface. The relative per­meability relationship assumed and especially the irreducible saturation of the gas phase greatly impacts predicted CO2 trapping mechanisms and long-term plume migration behavior. A primary goal of this study was to evaluate the impact of relative permeability on efficacy of regional-scale CO2 sequestration models. To accomplish this we built a 2-D vertical cross-section of the San Rafael Swell area of East-central Utah. This model simulated injection of CO2 into a brine aquifer for 30 years. The well was then shut-in and the CO2 plume behavior monitored for another 970 years. We evaluated five different relative permeability relationships to quantify their relative impacts on forecasted flow results of the model, with all other parameters maintained uniform and constant. Results of this analysis suggest that CO2 plume movement and behavior are significantly dependent on the specific relative permeability formulation assigned, including the assumed irreducible saturation values of CO2 and brine. More specifically, different relative permea­bility relationships translate to significant differences in CO2 plume behavior and corresponding trapping mechanisms.

The mechanics of delamination in fiber-reinforced composite materials. Part 2: Delamination behavior and fracture mechanics parameters

NASA Technical Reports Server (NTRS)

Wang, S. S.; Choi, I.

1983-01-01

Based on theories of laminate anisotropic elasticity and interlaminar fracture, the complete solution structure associated with a composite delamination is determined. Fracture mechanics parameters characterizing the interlaminar crack behavior are defined from asymptotic stress solutions for delaminations with different crack-tip deformation configurations. A numerical method employing singular finite elements is developed to study delaminations in fiber composites with any arbitrary combinations of lamination, material, geometric, and crack variables. The special finite elements include the exact delamination stress singularity in its formulation. The method is shown to be computationally accurate and efficient, and operationally simple. To illustrate the basic nature of composite delamination, solutions are shown for edge-delaminated (0/-0/-0/0) and (+ or - 0/+ or - 0/90/90 deg) graphite-epoxy systems under uniform axial extenstion. Three-dimensional crack-tip stress intensity factors, associated energy release rates, and delamination crack-closure are determined for each individual case. The basic mechanics and mechanisms of composite delamination are studied, and fundamental characteristics unique to recently proposed tests for interlaminar fracture toughness of fiber composite laminates are examined.

Microstructure, Mechanical Properties and Corrosion Behavior of Porous Mg-6 wt.% Zn Scaffolds for Bone Tissue Engineering

NASA Astrophysics Data System (ADS)

Yan, Yang; Kang, Yijun; Li, Ding; Yu, Kun; Xiao, Tao; Wang, Qiyuan; Deng, Youwen; Fang, Hongjie; Jiang, Dayue; Zhang, Yu

2018-03-01

Porous Mg-based scaffolds have been extensively researched as biodegradable implants due to their attractive biological and excellent mechanical properties. In this study, porous Mg-6 wt.% Zn scaffolds were prepared by powder metallurgy using ammonium bicarbonate particles as space-holder particles. The effects of space-holder particle content on the microstructure, mechanical properties and corrosion resistance of the Mg-6 wt.% Zn scaffolds were studied. The mean porosity and pore size of the open-cellular scaffolds were within the range 6.7-52.2% and 32.3-384.2 µm, respectively. Slight oxidation was observed at the grain boundaries and on the pore walls. The Mg-6 wt.% Zn scaffolds were shown to possess mechanical properties comparable with those of natural bone and had variable in vitro degradation rates. Increased content of space-holder particles negatively affected the mechanical behavior and corrosion resistance of the Mg-6 wt.% Zn scaffolds, especially when higher than 20%. These results suggest that porous Mg-6 wt.% Zn scaffolds are promising materials for application in bone tissue engineering.

Neural Network Models of Simple Mechanical Systems Illustrating the Feasibility of Accelerated Life Testing

NASA Technical Reports Server (NTRS)

Fusaro, Robert L.; Jones, Steven P.; Jansen, Ralph

1996-01-01

A complete evaluation of the tribological characteristics of a given material/mechanical system is a time-consuming operation since the friction and wear process is extremely systems sensitive. As a result, experimental designs (i.e., Latin Square, Taguchi) have been implemented in an attempt to not only reduce the total number of experimental combinations needed to fully characterize a material/mechanical system, but also to acquire life data for a system without having to perform an actual life test. Unfortunately, these experimental designs still require a great deal of experimental testing and the output does not always produce meaningful information. In order to further reduce the amount of experimental testing required, this study employs a computer neural network model to investigate different material/mechanical systems. The work focuses on the modeling of the wear behavior, while showing the feasibility of using neural networks to predict life data. The model is capable of defining which input variables will influence the tribological behavior of the particular material/mechanical system being studied based on the specifications of the overall system.

Hunger and thirst interact to regulate ingestive behavior in flies and mammals.

PubMed

Jourjine, Nicholas

2017-05-01

In animals, nervous systems regulate the ingestion of food and water in a manner that reflects internal metabolic need. While the coordination of these two ingestive behaviors is essential for homeostasis, it has been unclear how internal signals of hunger and thirst interact to effectively coordinate food and water ingestion. In the last year, work in insects and mammals has begun to elucidate some of these interactions. As reviewed here, these studies have identified novel molecular and neural mechanisms that coordinate the regulation of food and water ingestion behaviors. These mechanisms include peptide signals that modulate neural circuits for both thirst and hunger, neurons that regulate both food and water ingestion, and neurons that integrate sensory information about both food and water in the external world. These studies argue that a deeper understanding of hunger and thirst will require closer examination of how these two biological drives interact. © 2017 WILEY Periodicals, Inc.

Ash chemistry and sintering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skrifvars, B.J.; Backman, R.; Hupa, M.

1996-10-01

The chemistry of a fuel ash is important to consider when ash behavior in combustion or gasification is studied. Four different types of thermal behavior based bed agglomeration and deposit foliation mechanisms have been proposed to be important, (1) partial melting, (2) viscous flow, (3) chemical reaction sintering, and (4) solid state sintering. In this paper we present data from a broader study in which we have quantified the four mechanisms more in detail. The ashes from 10 different types of fuels have been tested for their sintering tendency by a compression strength sintering test. The ashes were also subjectmore » to quantitative wet chemical analyses and combined differential thermal, thermogravimetric (DT/TG) analyses. These thermal behavior predictions were compared with multi-component multi-phase thermodynamic phase equilibrium calculations and further with full scale combustion experience. The results and their relevance to full scale conversion systems are discussed in the paper.« less

An electrochemical study of the corrosion behavior of primer coated 2219-T87 aluminum

NASA Technical Reports Server (NTRS)

Danford, M. D.; Higgins, R. H.

1985-01-01

The corrosion behavior for 2219-T87 aluminum coated with various primers, including those used for the external tank and solid rocket boosters of the Space Shuttle Transportation System, were investigated using electrochemical techniques. Corrosion potential time, polarization resistance time, electrical resistance time, and corrosion rate time measurements were all investigated. It was found that electrical resistance time and corrosion rate time measurement were most useful for studying the corrosion behavior of painted aluminum. Electrical resistance time determination give useful information concerning the porosity of paint films, while corrosion rate time curves give important information concerning overall corrosion rates and corrosion mechanisms. In general, the corrosion rate time curves all exhibited at least one peak during the 30 day test period, which was attributed, according to the proposed mechanisms, to the onset of the hydrogen evolution reaction and the beginning of destruction of the protective properties of the paint film.

Neural mechanisms of movement planning: motor cortex and beyond.

PubMed

Svoboda, Karel; Li, Nuo

2018-04-01

Neurons in motor cortex and connected brain regions fire in anticipation of specific movements, long before movement occurs. This neural activity reflects internal processes by which the brain plans and executes volitional movements. The study of motor planning offers an opportunity to understand how the structure and dynamics of neural circuits support persistent internal states and how these states influence behavior. Recent advances in large-scale neural recordings are beginning to decipher the relationship of the dynamics of populations of neurons during motor planning and movements. New behavioral tasks in rodents, together with quantified perturbations, link dynamics in specific nodes of neural circuits to behavior. These studies reveal a neural network distributed across multiple brain regions that collectively supports motor planning. We review recent advances and highlight areas where further work is needed to achieve a deeper understanding of the mechanisms underlying motor planning and related cognitive processes. Copyright © 2017. Published by Elsevier Ltd.

Working Memory and Parent-Rated Components of Attention in Middle Childhood: A Behavioral Genetic Study

PubMed Central

Deater-Deckard, Kirby; Cutting, Laurie; Thompson, Lee A.; Petrill, Stephen A.

2012-01-01

The purpose of the current study was to investigate potential genetic and environmental correlations between working memory and three behavioral aspects of the attention network (i.e., executive, alerting, and orienting) using a twin design. Data were from 90 monozygotic (39% male) and 112 same-sex dizygotic (41% male) twins. Individual differences in working memory performance (digit span) and parent-rated measures of executive, alerting, and orienting attention included modest to moderate genetic variance, modest shared environmental variance, and modest to moderate nonshared environmental variance. As hypothesized, working memory performance was correlated with executive and alerting attention, but not orienting attention. The correlation between working memory, executive attention, and alerting attention was completely accounted for by overlapping genetic covariance, suggesting a common genetic mechanism or mechanisms underlying the links between working memory and certain parent-rated indicators of attentive behavior. PMID:21948215

Detecting the Biopolymer Behavior of Graphene Nanoribbons in Aqueous Solution

NASA Astrophysics Data System (ADS)

Wijeratne, Sithara S.; Penev, Evgeni S.; Lu, Wei; Li, Jingqiang; Duque, Amanda L.; Yakobson, Boris I.; Tour, James M.; Kiang, Ching-Hwa

2016-08-01

Graphene nanoribbons (GNR), can be prepared in bulk quantities for large-area applications by reducing the product from the lengthwise oxidative unzipping of multiwalled carbon nanotubes (MWNT). Recently, the biomaterials application of GNR has been explored, for example, in the pore to be used for DNA sequencing. Therefore, understanding the polymer behavior of GNR in solution is essential in predicting GNR interaction with biomaterials. Here, we report experimental studies of the solution-based mechanical properties of GNR and their parent products, graphene oxide nanoribbons (GONR). We used atomic force microscopy (AFM) to study their mechanical properties in solution and showed that GNR and GONR have similar force-extension behavior as in biopolymers such as proteins and DNA. The rigidity increases with reducing chemical functionalities. The similarities in rigidity and tunability between nanoribbons and biomolecules might enable the design and fabrication of GNR-biomimetic interfaces.

Detecting the Biopolymer Behavior of Graphene Nanoribbons in Aqueous Solution

PubMed Central

Wijeratne, Sithara S.; Penev, Evgeni S.; Lu, Wei; Li, Jingqiang; Duque, Amanda L.; Yakobson, Boris I.; Tour, James M.; Kiang, Ching-Hwa

2016-01-01

Graphene nanoribbons (GNR), can be prepared in bulk quantities for large-area applications by reducing the product from the lengthwise oxidative unzipping of multiwalled carbon nanotubes (MWNT). Recently, the biomaterials application of GNR has been explored, for example, in the pore to be used for DNA sequencing. Therefore, understanding the polymer behavior of GNR in solution is essential in predicting GNR interaction with biomaterials. Here, we report experimental studies of the solution-based mechanical properties of GNR and their parent products, graphene oxide nanoribbons (GONR). We used atomic force microscopy (AFM) to study their mechanical properties in solution and showed that GNR and GONR have similar force-extension behavior as in biopolymers such as proteins and DNA. The rigidity increases with reducing chemical functionalities. The similarities in rigidity and tunability between nanoribbons and biomolecules might enable the design and fabrication of GNR-biomimetic interfaces. PMID:27503635

Detecting the Biopolymer Behavior of Graphene Nanoribbons in Aqueous Solution

NASA Astrophysics Data System (ADS)

Li, Jingqiang; Wijeratne, Sithara; Penev, Evgeni; Lu, Wei; Duque, Amanda; Yakobson, Boris; Tour, James; Kiang, Ching-Hwa; Boris I. Yakobson Group Team; James M. Tour Group Team; Ching-Hwa Kiang Group Team

Graphene nanoribbons (GNR), can be prepared in bulk quantities for large-area applications by reducing the product from the lengthwise oxidative unzipping of multiwalled carbon nanotubes (MWNT). Recently, the biomaterials application of GNR has been explored, for example, in the pore to be used for DNA sequencing. Therefore, understanding the polymer behavior of GNR in solution is essential in predicting GNR interaction with biomaterials. Here, we report experimental studies of the solutionbased mechanical properties of GNR and their parent products, graphene oxide nanoribbons (GONR). We used atomic force microscopy (AFM) to study their mechanical properties in solution and showed that GNR and GONR have similar force-extension behavior as in biopolymers such as proteins and DNA. The rigidity increases with reducing chemical functionalities. The similarities in rigidity and tunability between nanoribbons and biomolecules might enable the design and fabrication of GNR-biomimetic interfaces.

HMSPP nanocomposite and Brazilian bentonite properties after gamma radiation exposure

NASA Astrophysics Data System (ADS)

Fermino, D. M.; Parra, D. F.; Oliani, W. L.; Lugao, A. B.; Díaz, F. R. V.

2013-03-01

This work concerns the study of the mechanical and thermal behavior of the nanocomposite high melt strength polypropylene (HMSPP) (obtained at a dose of 12.5 kGy) and a bentonite clay Brazilian Paraiba (PB), which is known as "chocolate" and is used in concentrations of 5% and 10% by weight, in comparison to the American Cloisite 20A clay nanocomposites. An agent compatibilizer polypropylene-graft (PP-g-AM) was added at a 3% concentration, and the clay was dispersed using the melt intercalation technique using a twin-screw extruder. The specimens were prepared by the injection process. The mechanical behavior was evaluated by strength, flexural strength and impact tests. The thermal behavior was evaluated by the techniques of differential scanning calorimetry (DSC) and thermogravimetry (TGA). The morphology of the nanocomposites was studied with scanning electron microscopy (SEM), while the organophilic bentonite and nanocomposites were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR).

The Addictive Model of Self-Harming (Non-suicidal and Suicidal) Behavior.

PubMed

Blasco-Fontecilla, Hilario; Fernández-Fernández, Roberto; Colino, Laura; Fajardo, Lourdes; Perteguer-Barrio, Rosa; de Leon, Jose

2016-01-01

Behavioral addictions such as gambling, sun-tanning, shopping, Internet use, work, exercise, or even love and sex are frequent, and share many characteristics and common neurobiological and genetic underpinnings with substance addictions (i.e., tolerance, withdrawal, and relapse). Recent literature suggests that both non-suicidal self-injury (NSSI) and suicidal behavior (SB) can also be conceptualized as addictions. The major aim of this mini review is to review the literature and explore the neurobiological and psychological mechanisms underlying the addiction to self-harming behaviors. This is a narrative review. The authors performed literature searches in PubMed and Google for suicidal behavior, self-harming, addiction, and "major repeaters." Given the scarce literature on the topic, a subset of the most closely related studies was selected. The authors also focused on three empirical studies testing the hypothesis that major repeaters (individuals with ≥5 lifetime suicide attempts) represent a distinctive suicidal phenotype and are the individuals at risk of developing an addiction to SB. The authors reviewed the concept of behavioral addictions and major repeaters, current empirical evidence testing concerning whether or not NSSI and SB can be understood as "addictions," and the putative mechanisms underlying them. Our review suggests that both NSSI and SB can be conceptualized as addictions. This is relevant because if some individual's self-harming behaviors are better conceptualized as an addiction, treatment approaches could be tailored to this addiction.

Rat disc torsional mechanics: effect of lumbar and caudal levels and axial compression load.

PubMed

Espinoza Orías, Alejandro A; Malhotra, Neil R; Elliott, Dawn M

2009-03-01

Rat models with altered loading are used to study disc degeneration and mechano-transduction. Given the prominent role of mechanics in disc function and degeneration, it is critical to measure mechanical behavior to evaluate changes after model interventions. Axial compression mechanics of the rat disc are representative of the human disc when normalized by geometry, and differences between the lumbar and caudal disc have been quantified in axial compression. No study has quantified rat disc torsional mechanics. Compare the torsional mechanical behavior of rat lumbar and caudal discs, determine the contribution of combined axial load on torsional mechanics, and compare the torsional properties of rat discs to human lumbar discs. Cadaveric biomechanical study. Cyclic torsion without compressive load followed by cyclic torsion with a fixed compressive load was applied to rat lumbar and caudal disc levels. The apparent torsional modulus was higher in the lumbar region than in the caudal region: 0.081+/-0.026 (MPa/degrees, mean+/-SD) for lumbar axially loaded; 0.066+/-0.028 for caudal axially loaded; 0.091+/-0.033 for lumbar in pure torsion; and 0.056+/-0.035 for caudal in pure torsion. These values were similar to human disc properties reported in the literature ranging from 0.024 to 0.21 MPa/degrees. Use of the caudal disc as a model may be appropriate if the mechanical focus is within the linear region of the loading regime. These results provide support for use of this animal model in basic science studies with respect to torsional mechanics.

Attitude toward money modulates outcome processing: an ERP study.

PubMed

Jia, Shiwei; Zhang, Wenxin; Li, Peng; Feng, Tingyong; Li, Hong

2013-01-01

Love of money (LOM) is concerned with the attitude toward money, which can be measured by the LOM scale through affective, behavioral, and cognitive dimensions. Research has observed that monetary attitude was tightly related to reward processing and could affect economic behavior. This study examined how monetary attitude modulated risky behavior and the underlying neural mechanisms of reward processing using event-related potential (ERP) technique. We compared both the risk level and brain responses of a high-level LOM (HLOM) group to a low-level LOM (LLOM) group using a simple gambling task. The behavioral results showed that the HLOM group was more risky than the LLOM group, particularly after loss. The feedback-related negativity (FRN) was measured as the difference wave (gain-related ERP was subtracted from loss-related ERP). The FRN difference wave was larger in the HLOM group than that in the LLOM group. The P3 in the HLOM group was more positive than that in the LLOM group. These results suggest that monetary attitude can modulate both the underlying neural mechanisms and behavioral performance in a reward-related task. The HLOM participants are more sensitive to gain/loss than the LLOM participants.

Smartphone users: Understanding how security mechanisms are perceived and new persuasive methods

PubMed Central

Alsaleh, Mansour; Alomar, Noura; Alarifi, Abdulrahman

2017-01-01

Protecting smartphones against security threats is a multidimensional problem involving human and technological factors. This study investigates how smartphone users’ security- and privacy-related decisions are influenced by their attitudes, perceptions, and understanding of various security threats. In this work, we seek to provide quantified insights into smartphone users’ behavior toward multiple key security features including locking mechanisms, application repositories, mobile instant messaging, and smartphone location services. To the best of our knowledge, this is the first study that reveals often unforeseen correlations and dependencies between various privacy- and security-related behaviors. Our work also provides evidence that making correct security decisions might not necessarily correlate with individuals’ awareness of the consequences of security threats. By comparing participants’ behavior and their motives for adopting or ignoring certain security practices, we suggest implementing additional persuasive approaches that focus on addressing social and technological aspects of the problem. On the basis of our findings and the results presented in the literature, we identify the factors that might influence smartphone users’ security behaviors. We then use our understanding of what might drive and influence significant behavioral changes to propose several platform design modifications that we believe could improve the security levels of smartphones. PMID:28297719