scholarly journals Mechanics unlocks the morphogenetic puzzle of interlocking bivalved shells

2019 ◽  
Vol 117 (1) ◽  
pp. 43-51 ◽  
Author(s):  
Derek E. Moulton ◽  
Alain Goriely ◽  
Régis Chirat
Keyword(s):  
Pattern Formation ◽  
Growth Process ◽  
Shell Growth ◽  
Point Of View ◽  
Mathematical Framework ◽  
Bivalve Mollusks ◽  
Modeling Framework ◽  
Mechanistic Basis ◽  
Developmental Point ◽  
Rigid Shell

Brachiopods and mollusks are 2 shell-bearing phyla that diverged from a common shell-less ancestor more than 540 million years ago. Brachiopods and bivalve mollusks have also convergently evolved a bivalved shell that displays an apparently mundane, yet striking feature from a developmental point of view: When the shell is closed, the 2 valve edges meet each other in a commissure that forms a continuum with no gaps or overlaps despite the fact that each valve, secreted by 2 mantle lobes, may present antisymmetric ornamental patterns of varying regularity and size. Interlocking is maintained throughout the entirety of development, even when the shell edge exhibits significant irregularity due to injury or other environmental influences, which suggests a dynamic physical process of pattern formation that cannot be genetically specified. Here, we derive a mathematical framework, based on the physics of shell growth, to explain how this interlocking pattern is created and regulated by mechanical instabilities. By close consideration of the geometry and mechanics of 2 lobes of the mantle, constrained both by the rigid shell that they secrete and by each other, we uncover the mechanistic basis for the interlocking pattern. Our modeling framework recovers and explains a large diversity of shell forms and highlights how parametric variations in the growth process result in morphological variation. Beyond the basic interlocking mechanism, we also consider the intricate and striking multiscale-patterned edge in certain brachiopods. We show that this pattern can be explained as a secondary instability that matches morphological trends and data.

scholarly journals QUANTUM SINGULARITIES IN STATIC SPACETIMES

2011 ◽  
Vol 20 (05) ◽  
pp. 729-743 ◽  
Author(s):  
JOÃO PAULO M. PITELLI ◽  
PATRICIO S. LETELIER
Keyword(s):  
Quantum Mechanics ◽  
Wave Operator ◽  
Point Of View ◽  
Quantum Mechanical ◽  
Mathematical Framework ◽  
Physical Content ◽  
Dirac Equations ◽  
Quantum Particles ◽  
Klein Gordon ◽  
Quantum Singularities

We review the mathematical framework necessary to understand the physical content of quantum singularities in static spacetimes. We present many examples of classical singular spacetimes and study their singularities by using wave packets satisfying Klein–Gordon and Dirac equations. We show that in many cases the classical singularities are excluded when tested by quantum particles but unfortunately there are other cases where the singularities remain from the quantum mechanical point of view. When it is possible we also find, for spacetimes where quantum mechanics does not exclude the singularities, the boundary conditions necessary to turn the spatial portion of the wave operator to be self-adjoint and emphasize their importance to the interpretation of quantum singularities.

scholarly journals Adolesence and Family Crises

1968 ◽  
Vol 13 (2) ◽  
pp. 125-133 ◽  
Author(s):  
Donald G. Langsley ◽  
Robert H. Fairbairn ◽  
Carol D. Deyoung
Keyword(s):  
Family Member ◽  
Point Of View ◽  
Tension Reduction ◽  
Therapy Approach ◽  
Family Crisis ◽  
The Family ◽  
Adaptive Solution ◽  
Developmental Point ◽  
The Individual

Like the individual, the family may be better understood from a developmental point of view. It has different tasks and problems at various stages of its existence. The family with adolescent children faces a change in composition (loss of children and the responsibility of helping these children become adults). This threat may produce a family crisis and individual members may react to the specific conflicts in a manner which depends on their previous problems. The family member who becomes a ‘patient’ may be the teenager or a parent. A family crisis therapy approach permits tension reduction within the group, improves functioning on the part of the ‘patient’ and permits the family to work out a more adaptive solution.

Pattern formation and pattern selection in the Landau–Ginzburg model of critical phenomena

1990 ◽  
Vol 68 (9) ◽  
pp. 760-767 ◽  
Author(s):  
J. A. Tuszynski ◽  
M. Otwinowski
Keyword(s):  
Liquid Crystals ◽  
Partial Differential Equations ◽  
Pattern Formation ◽  
Critical Phenomena ◽  
Nonlinear Partial Differential Equations ◽  
Point Of View ◽  
Pattern Selection ◽  
Control Parameters ◽  
The Family ◽  
Kinetics Of

In this paper we investigate the family of nonlinear partial differential equations used to describe the kinetics of critical phenomena within the Landau–Ginzburg model. An analysis of the recently obtained symmetry-reduction results for a number of such equations is provided from the point of view of pattern formation at criticality. Various possibilities occur depending on the choice of control parameters. An illustration is provided using several physical examples such as metamagnets and liquid crystals.

EFFECT OF EARLY FEEDING OF SOLID FOODS ON NUTRITIVE INTAKE OF INFANTS

PEDIATRICS ◽  
1966 ◽  
Vol 38 (5) ◽  
pp. 879-885
Author(s):  
Helen A. Guthrie
Keyword(s):  
National Research Council ◽  
Point Of View ◽  
Caloric Content ◽  
Early Feeding ◽  
Cereal Products ◽  
Early Introduction ◽  
Solid Foods ◽  
Developmental Point ◽  
The Cost ◽  
Current Emphasis

The early introduction of solid foods to the diet of bottle-fed infants living in a college town causes some significant changes in the nutritive content of the diet but does not increase the adequacy of the diet before 3 months as evaluated by allowances recommended for infants by the National Research Council. Diets containing solid foods provide significantly more iron and thiamine, two of the nutrients used to enrich infant cereal products. Most of the infants were receiving nutritional supplements of vitamin A and D in spite of the fact that their diets were adequate in these nutrients. The need for a supplement of ascorbic acid was evident for some infants. The feeding of solid foods apparently had no effect on the sleeping pattern of the infants as evidenced by the number of feedings, nor did it increase the cost of the food itself. It did, however, increase the time and effort involved for the mother. Since there was no increase in the caloric content of the diet, the solid foods must have replaced milk rather then to have supplemented it, a fact confirmed by the observations of many mothers. At least 10% of the infants experienced some form of allergic reaction to solid foods. All of the infants in the study had been introduced to solid foods by 9 weeks, 2 to 4 weeks prior to the age at which the American Academy of Pediatrics suggests that there is a rational basis from a nutritional and developmental point of view to begin supplementing the diet. Although there was no evidence of adverse reactions other then allergies to the pattern of early feeding observed in this group, there was no evidence to indicate that the infant benefitted from a nutritional standpoint. Lack of evidence of benefits and an accumulating body of information on hazards from the early introduction of solid foods suggest a re-examination of current emphasis on the early supplementation of the milk diet in infants.

scholarly journals Mathematical modeling of bone in-growth into undegradable porous periodic scaffolds under mechanical stimulus

2019 ◽  
Vol 10 ◽  
pp. 204173141982716 ◽  
Author(s):  
Lingze Liu ◽  
Quan Shi ◽  
Qiang Chen ◽  
Zhiyong Li
Keyword(s):  
Mathematical Modeling ◽  
Bone Formation ◽  
Growth Process ◽  
Bone Repair ◽  
Mechanical Stimulus ◽  
Clinical Applications ◽  
Mathematical Framework ◽  
Paracrine Effects ◽  
Clinical Observations ◽  
Coupling Cell

Undegradable scaffolds, as a key element in bone tissue engineering, prevail in the present clinical applications, and the bone in-growth into such scaffolds under mechanical stimulus is an important issue to evaluate the bone-repair effect. This work aims to develop a mathematical framework to investigate the effect of mechanical stimulus on the bone in-growth into undegradable scaffolds. First, the osteoclast and osteoblast activities were coupled by their autocrine and paracrine effects. Second, the mechanical stimulus was empirically incorporated into the coupling cell activities on the basis of experimental observations. Third, the effect of mechanical stimulus including intensity and duration on the bone in-growth process was numerically studied; moreover, the homeostasis of scaffold–bone system under the mechanical stimulus was also treated. The results showed that the numbers of osteoblasts and osteoclasts in the scaffold–bone system tended to constants representing the system homeostasis. Both the mechanical intensity and duration optimized the final bone formation. The numerical results of the bone formation were comparable to the experimental results in rats. The findings from this modeling study could be used to explain many physiological phenomena and clinical observations. The developed model integrates both cell and tissue scales, which can be used as a platform to investigate bone remodeling under mechanical stimulus.

Aromatic thiol-modulated Ag overgrowth on gold nanoparticles: tracking the thiol's position in the core–shell nanoparticles

Nanoscale ◽  
2019 ◽  
Vol 11 (37) ◽  
pp. 17471-17477 ◽  
Author(s):  
Jiaqi Chen ◽  
Dejing Meng ◽  
Hui Wang ◽  
Haiyun Li ◽  
Yinglu Ji ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Growth Process ◽  
Shell Growth ◽  
Core Shell ◽  
Internal Reference ◽  
Shell Nanoparticles ◽  
Aromatic Thiol ◽  
The Core ◽  
Spatial Trajectory ◽  
Core Shell Nanoparticles

Using DMAB as the Raman internal reference, the spatial trajectory of modulating 4-ATP molecules was tracked during the shell growth process.

scholarly journals Successful ageing and development: the contribution of generativity in older age

2011 ◽  
Vol 32 (7) ◽  
pp. 1087-1105 ◽  
Author(s):  
FELICIANO VILLAR
Keyword(s):  
Social Context ◽  
Personal Growth ◽  
Point Of View ◽  
Older Age ◽  
Successful Ageing ◽  
Specific Content ◽  
Clinical Criteria ◽  
The Social ◽  
Adaptive Processes ◽  
Developmental Point

ABSTRACTThis paper examines the contributions that generativity in older age may make to the concept of successful ageing. To this end, two perspectives on successful ageing are described: successful ageing as a set of clinical criteria, and successful ageing as the application of adaptive processes aimed at achieving efficient functioning. After showing the limitations of the first perspective, particularly from a developmental point of view, the paper argues that the adaptive version of successful ageing helps to put ageing into a developmental frame, but needs to be complemented by identifying specific content and goals that guide these adaptive processes and establish new feasible gains for older people. Generativity in older age could play that role and provides a conceptual framework that enriches the concept of successful ageing, both by emphasising the social context in which people age and by highlighting a personal growth component.

Development of interpersonal trust among children and adolescents

2012 ◽  
Vol 43 (1) ◽  
pp. 50-58 ◽  
Author(s):  
Małgorzata Szcześniak ◽  
Melusina Colaço ◽  
Gloria Rondón
Keyword(s):  
Children And Adolescents ◽  
Interpersonal Trust ◽  
Academic Discipline ◽  
Empirical Studies ◽  
Three Dimensional ◽  
Point Of View ◽  
School Age Children ◽  
The Past ◽  
Human Functioning ◽  
Developmental Point

Development of interpersonal trust among children and adolescentsThe main purpose of the present article is to introduce a topic related to the development of interpersonal trust among children and adolescents. Although this subject, since the beginnings of psychology considered as an academic discipline, has been regarded as an essential component of human functioning, there are still very few theoretical and empirical studies that approach the issue from a developmental point of view. In this paper the three-dimensional conceptualization of interpersonal trust is provided. Furthermore, the article highlights the past and current theoretical and empirical research on the development of interpersonal trust in infants, preschool and school-age children. Finally, some challenges are presented in the field of interpersonal trust studies.

scholarly journals Lexical, Morphological, and Syntactic Characteristics of Verbs in the Spontaneous Production of Italian Children

2011 ◽  
Vol 2011 ◽  
pp. 1-17 ◽  
Author(s):  
Laura D'Odorico ◽  
Mirco Fasolo ◽  
Rosalinda Cassibba ◽  
Alessandro Costantini
Keyword(s):  
Language Acquisition ◽  
Early Period ◽  
Point Of View ◽  
Spontaneous Production ◽  
Abstract Knowledge ◽  
Different Types ◽  
Relative Production ◽  
Developmental Point ◽  
Italian Children ◽  
Mean Length Of Utterance

This study investigates from a developmental point of view the lexical, morphological, and syntactic characteristics of verb production during the first stages of language acquisition. The spontaneous productions of children with different mean length of utterance (MLU) were analysed, examining the relative production of different types of verbs (transitive, intransitive, and mixed), the arguments expressed or omitted in the utterances containing a verb, the morphological inflections produced by the children for each verb, and the generalisation of the syntactic construction with which specific verbs were produced. Data are interpreted in support of the hypothesis that children have a limited abstract knowledge of verbs in the early period of multiword utterance production and that the process of abstractness and generalisation develops gradually on the basis of linguistic experience.

Sign in / Sign up

Export Citation Format

Share Document