scholarly journals Compete or Coexist? Why the Same Mechanisms of Symmetry Breaking Can Yield Distinct Outcomes

Cells ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 2011 ◽  
Author(s):  
Andrew B. Goryachev ◽  
Marcin Leda
Keyword(s):  
Symmetry Breaking ◽  
Theoretical Models ◽  
Small Gtpases ◽  
Cellular Structures ◽  
Mathematical Apparatus ◽  
Cellular Morphogenesis ◽  
Multiple Structures ◽  
The Common ◽  
Kinetics Of ◽  
Theoretical Analyses

Cellular morphogenesis is governed by the prepattern based on the symmetry-breaking emergence of dense protein clusters. Thus, a cluster of active GTPase Cdc42 marks the site of nascent bud in the baker’s yeast. An important biological question is which mechanisms control the number of pattern maxima (spots) and, thus, the number of nascent cellular structures. Distinct flavors of theoretical models seem to suggest different predictions. While the classical Turing scenario leads to an array of stably coexisting multiple structures, mass-conserved models predict formation of a single spot that emerges via the greedy competition between the pattern maxima for the common molecular resources. Both the outcome and the kinetics of this competition are of significant biological importance but remained poorly explored. Recent theoretical analyses largely addressed these questions, but their results have not yet been fully appreciated by the broad biological community. Keeping mathematical apparatus and jargon to the minimum, we review the main conclusions of these analyses with their biological implications in mind. Focusing on the specific example of pattern formation by small GTPases, we speculate on the features of the patterning mechanisms that bypass competition and favor formation of multiple coexisting structures and contrast them with those of the mechanisms that harness competition to form unique cellular structures.

The Problem of the Typology of Rationality in Muslim Culture

2019 ◽  
Vol 62 (6) ◽  
pp. 88-99
Author(s):  
Andrey A. Lukashev
Keyword(s):  
Modern Philosophy ◽  
Theoretical Basis ◽  
Theoretical Models ◽  
The Other ◽  
Common Denominator ◽  
Islamic Culture ◽  
The Common ◽  
Per Se ◽  
The One ◽  
Muslim Culture

The typology of rationality is one of major issues of modern philosophy. In an attempt to provide a typology to Oriental materials, a researcher faces additional problems. The diversity of the Orient as such poses a major challenge. When we say “Oriental,” we mean several cultures for which we cannot find a common denominator. The concept of “Orient” involves Arabic, Indian, Chinese, Turkish and other cultures, and the only thing they share is that they are “non-Western.” Moreover, even if we focus just on Islamic culture and look into rationality in this context, we have to deal with a conglomerate of various trends, which does not let us define, with full confidence, a common theoretical basis and treat them as a unity. Nevertheless, we have to go on trying to find common directions in thought development, so as to draw conclusions about types of rationality possible in Islamic culture. A basis for such a typology of rationality in the context of the Islamic world was recently suggested in A.V. Smirnov’s logic of sense theory. However, actual empiric material cannot always fit theoretical models, and the cases that do not fit the common scheme are interesting per se. On the one hand, examination of such cases gives an opportunity to specify certain provisions of the theory and, on the other hand, to define the limits of its applicability.

Kinetics of hypso anhydrites dissolution in water. Experimental studies

2019 ◽  
pp. 93-96
Author(s):  
A. L. Lebedev ◽  
I. V. Avilina
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Riccati Equation ◽  
Balance Equation ◽  
Experimental Studies ◽  
Common Ion ◽  
The Common ◽  
Common Ion Effect ◽  
Kinetics Of Dissolution ◽  
Kinetics Of

Experimental study of kinetics of dissolution of hypso anhydrites at 25 ᵒC made it possible to formulate model of the process in the form of a balance equation for the kinetics of dissolution of gypsum, anhydrite (first and second orders, respectively) and kinetics of precipitation of gypsum (second order). The processing of the experimental data were carried out on the basis of the solution of the Riccati equation. When taking into account the common-ion effect on the solubility of gypsum and anhydrite, the calculated values turned out to be more comparable with the experimental ones.

scholarly journals Multi-attribute Decision-making is Best Characterized by an Attribute-Wise Reinforcement Learning Model

2017 ◽  
Author(s):  
Shaoming Wang ◽  
Bob Rehder
Keyword(s):  
Computational Models ◽  
Theoretical Models ◽  
Decision Makers ◽  
Common Finding ◽  
Cue Competition ◽  
Recency Effects ◽  
Multiple Attribute ◽  
Multi Attribute Decision Making ◽  
The Common ◽  
Alternative Choice

AbstractChoice alternatives often consist of multiple attributes that vary in how successfully they predict reward. Some standard theoretical models assert that decision makers evaluate choices either by weighting those attribute optimally in light of previous experience (so-called rational models), or adopting heuristics that use attributes suboptimally but in a manner that yields reasonable performance at minimal cost (e.g., the take-the-best heuristic). However, these models ignore both the possibility that decision makers might learn to associate reward with whole stimuli (a particular combination of attributes) rather than individual attributes and the common finding that decisions can be overly influenced by recent experiences and exhibit cue competition effects. Participants completed a two-alternative choice task where each stimulus consisted of three binary attributes that were predictive of reward, albeit with different degrees of reliability. Their choices revealed that, rather than using only the “best” attribute, they made use of all attributes but in manner that reflected the classic cue competition effect known as overshadowing. The time needed to make decisions increased as the number of relevant attributes increased, suggesting that reward was associated with attributes rather than whole stimuli. Fitting a family of computational models formed by crossing attribute use (optimal vs. only the best), representation (attribute vs. whole stimuli), and recency (biased or not), revealed that models that performed better when they made use of all information, represented attributes, and incorporated recency effects and cue competition. We also discuss the need to incorporate selective attention and hypothesis-testing like processes to account for results with multiple-attribute stimuli.

scholarly journals Theoretical Models for Interpreting the Dielectric Behaviour of HF-doped Ice

1978 ◽  
Vol 21 (85) ◽  
pp. 123-141 ◽  
Author(s):  
G. C. Camplin ◽  
J. W. Glen ◽  
J. G. Paren
Keyword(s):  
Single Crystals ◽  
Electrical Conduction ◽  
Fluoride Concentration ◽  
Theoretical Models ◽  
Data Set ◽  
Wide Range ◽  
Yield Values ◽  
Full Knowledge ◽  
The Common ◽  
Ice Lattice

AbstractTo understand the recent dielectric measurements made on HF-doped ice single crystals requires a full knowledge of the concentration of electrical defects present in ice and their subsequent interactions. Previous interpretations of the behaviour of HF-doped ice have concentrated upon specific features in isolation, whereas this paper presents analyses of a data set of 139 temperature and impurity combinations from 17 HF-doped ice single crystals. The interpretation of the behaviour of these crystals is in terms of several possible theoretical models. All models are based upon the common assumptions that HF molecules enter the ice lattice substitutionally and that excess Bjerrum and ionic defects can be formed at the HF sites. They also use the theory of electrical conduction in ice by Jaccard (1959) and the defect equilibria analysis in ice by Kroger (1974).All models yield values for the concentration, mobility, energy of formation and charges for the different types of electrical defect considered to be generated.From the model which assumes that only three fluorine centres exist, the approximate derived values of the mobility and charge for the L-defect and positive ionic defect are as follows: μL = 5 × 10-8 m2 V-1 s-1 at 273 K, eDL = 0.44e; μ+ = 2.7 × 10-8 m2 V-1 s-1 at 273 K, e± 0.73e.Finally, using the derived defect conductivities and the Jaccard theory of electrical conduction, the relaxation tune of HF-doped ice has been successfully predicted over a wide range of temperature and fluoride concentration.

Angiotensin converting enzyme in brush-border membranes of avian small intestine

1988 ◽  
Vol 135 (1) ◽  
pp. 1-8
Author(s):  
B. R. Stevens ◽  
A. Fernandez ◽  
C. del Rio Martinez
Keyword(s):  
Angiotensin Converting Enzyme ◽  
Brush Border ◽  
Physiological Role ◽  
Intestinal Epithelial ◽  
Converting Enzyme ◽  
Brush Border Membranes ◽  
Fluid Uptake ◽  
The Common ◽  
Kinetics Of ◽  
Hydrolysis Of

Angiotensin converting enzyme activity was identified in brush-border membranes purified from the small intestinal epithelium of the common grackle, Quiscalus quiscula. Angiotensin converting enzyme was enriched 20-fold in the membrane preparation, compared with intestinal epithelial cell scrapes, and was coenriched with the brush-border markers, alkaline phosphatase and aminopeptidase N. The kinetics of hydrolysis of N-[3-(2-furyl)acryloyl]-L-phenylalanylglycylglycine (FAPGG) gave a Vmax of 907 +/− 41 units g-1 and a Km of 55 +/− 6 mumol l-1. The avian intestinal angiotensin converting enzyme was inhibited by the antihypertensive drug, Ramipril, with a median inhibitory concentration (IC50) of 1 nmol l-1. In the light of previous studies on angiotensin converting enzyme in mammalian epithelia, these results may implicate a physiological role for angiotensin converting enzyme in regulating electrolyte and fluid uptake in bird small intestines.

scholarly journals Development of a Vaping Machine for the Sampling of THC and CBD Aerosols Generated by Two Portable Dry Herb Cannabis Vaporisers

2020 ◽  
Vol 3 (1) ◽  
pp. 84-94 ◽  
Author(s):  
Laura Carrara ◽  
Christian Giroud ◽  
Nicolas Concha-Lozano
Keyword(s):  
Cannabis Sativa ◽  
Therapeutic Potential ◽  
Electronic Cigarettes ◽  
Immediate Release ◽  
Self Medication ◽  
Extraction Coefficient ◽  
Adverse Health Effects ◽  
The Common ◽  
Recreational Use ◽  
Kinetics Of

Cannabis sativa is known for its recreational use, but also for its therapeutic potential. There has been wide discussion over the use of cannabis for medical purposes in recent years, especially because a consensus has not been reached regarding its risk/benefit balance. Among the more common modes of administration, vaping with a vaporiser is most frequently used for self-medication. Vaping seems to be a better alternative to preventing adverse health effects due to toxic compounds produced during combustion when cannabis is smoked. However, the delivery kinetics and efficiency of most portable vaporisers are not fully characterised with an appropriate vaping regime. This determination requires a specific vaping machine operating under realistic puffing conditions. In this study, a vaping machine was conceived to fit with the common uses of portable vaporisers that requires conditions different from those used for electronic cigarettes. The experimental setup in this study was optimised to sample aerosolised cannabinoids. The delivery kinetics, efficiency, and decarboxylation yields of two commercially available vaporisers (DaVinci® and Mighty Medic®) were evaluated for delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). Among all tested sampling supports, the glass fibre filter is the most efficient medium to collect mixed THC and CBD aerosols. From the delivery kinetics of cannabinoids, a single-parameter model was used to calculate the extraction coefficient of each vaporiser. The results show that the Mighty Medic® vaporiser had a higher extraction coefficient (0.39) and a more immediate release of cannabinoids than the DaVinci® vaporiser (0.16), which had a gradual and slower rate of vaporisation. This parameter could be a quantitative input in pharmacokinetic models of administration of volatile compounds using vaporisers and a useful tool for the comparison of vaporisers.

scholarly journals Spontaneous and Controlled Macroscopic Chiral Symmetry Breaking by Means of Crystallization

Symmetry ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 1796
Author(s):  
Gérard Coquerel ◽  
Marine Hoquante
Keyword(s):  
Symmetry Breaking ◽  
Chiral Symmetry ◽  
Chiral Symmetry Breaking ◽  
Operating Conditions ◽  
Temperature Cycle ◽  
Final State ◽  
Open Questions ◽  
The Impact ◽  
Kinetics Of ◽  
Influential Parameters

In this paper, macroscopic chiral symmetry breaking refers to as the process in which a mixture of enantiomers departs from 50–50 symmetry to favor one chirality, resulting in either a scalemic mixture or a pure enantiomer. In this domain, crystallization offers various possibilities, from the classical Viedma ripening or Temperature Cycle-Induced Deracemization to the famous Kondepudi experiment and then to so-called Preferential Enrichment. These processes, together with some variants, will be depicted in terms of thermodynamic pathways, departure from equilibrium and operating conditions. Influential parameters on the final state will be reviewed as well as the impact of kinetics of the R ⇔ S equilibrium in solution on chiral symmetry breaking. How one can control the outcome of symmetry breaking is examined. Several open questions are detailed and different interpretations are discussed.

Microstructure Evolution in the Atomized Droplets of Mg-9wt%Al Alloy

2010 ◽  
Vol 146-147 ◽  
pp. 1094-1101
Author(s):  
Fei Ding ◽  
Xiao Feng Wang
Keyword(s):  
Droplet Size ◽  
Microstructure Evolution ◽  
Eutectic Reaction ◽  
Solidification Process ◽  
Nucleation And Growth ◽  
Al Alloy ◽  
Microstructure Development ◽  
The Common ◽  
Kinetics Of ◽  
Common Action

A numerical model is developed to describe the kinetics of the microstructure evolution in an atomized droplet of Mg-9wt%Al alloy. The model is coupled with the heat transfer controlling equations to simulate the solidification process of the atomized droplets. The numerical results show that the microstructure development is a result of the common action of the nucleation and growth of grains. The nucleation events take place at a critical supercooling for a given droplet. As the droplet size decreases, the critical supercooling increases significantly. The volume fractions of the phases formed during the period of the recalescence, the segregated solidification and the eutectic reaction are sensitive to the droplet size. It is demonstrated that the developed model describes the microstructure evolution process well.

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