Revising Inconsistent Concepts

2017 ◽  
Author(s):  
Kevin Scharp ◽  
Stewart Shapiro ◽  
Bradley Armour-Garb
Keyword(s):  
Fundamental Question ◽  
Concept Of Truth ◽  
Constitutive Principles ◽  
Insight Into

This chapter investigates the question of when it is reasonable to replace an inconsistent concept. After surveying a number of proposals for how one might understand constitutive principles, it goes on to endorse Burgess’s (2004) account of being pragmatically analytic, as a possible source of insight into constitutive principles. The chapter then raises a question: If truth is an inconsistent concept, does it need to be replaced? According to the argument in the chapter, when an inconsistent concept paralyzes valuable projects, it is time to replace it. And if we are to replace a concept, our replacement should be able to do the work that the inconsistency-yielding one did. This, of course, raises a fundamental question concerning what work the notion of truth does for us. The chapter mounts a case for the claim that inflationists, but not obvious deflationists, about truth should offer a replacement for the concept of truth.

scholarly journals How cells determine the number of polarity sites

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Jian-geng Chiou ◽  
Kyle D Moran ◽  
Daniel J Lew
Keyword(s):  
Design Principle ◽  
Fundamental Question ◽  
Yeast Cells ◽  
Regulatory Mechanisms ◽  
Saturation Point ◽  
Rho Family Gtpases ◽  
Rho Family ◽  
Theoretical Analyses ◽  
Novel Design ◽  
Insight Into

The diversity of cell morphologies arises, in part, through regulation of cell polarity by Rho-family GTPases. A poorly understood but fundamental question concerns the regulatory mechanisms by which different cells generate different numbers of polarity sites. Mass-conserved activator-substrate (MCAS) models that describe polarity circuits develop multiple initial polarity sites, but then those sites engage in competition, leaving a single winner. Theoretical analyses predicted that competition would slow dramatically as GTPase concentrations at different polarity sites increase towards a 'saturation point', allowing polarity sites to coexist. Here, we test this prediction using budding yeast cells, and confirm that increasing the amount of key polarity proteins results in multiple polarity sites and simultaneous budding. Further, we elucidate a novel design principle whereby cells can switch from competition to equalization among polarity sites. These findings provide insight into how cells with diverse morphologies may determine the number of polarity sites.

scholarly journals Xenopus hybrids provide insight into cell and organism size control

2018 ◽  
Author(s):  
Romain Gibeaux ◽  
Kelly Miller ◽  
Rachael Acker ◽  
Taejoon Kwon ◽  
Rebecca Heald
Keyword(s):  
Gene Expression ◽  
Cell Size ◽  
Size Control ◽  
Fundamental Question ◽  
Scaling Relationships ◽  
Tailbud Stage ◽  
Differential Gene ◽  
Genome Activation ◽  
Insight Into ◽  
Zygotic Genome

AbstractDetermining how size is controlled is a fundamental question in biology that is poorly understood at the organismal, cellular and subcellular levels. The Xenopus species, X. laevis and X. tropicalis differ in size at all three of these levels. Despite these differences, fertilization of X. laevis eggs with X. tropicalis sperm gives rise to viable hybrid animals that are intermediate in size. We observed that although hybrid and X. laevis embryogenesis initiates from the same sized zygote and proceeds synchronously through development, hybrid animals were smaller by the tailbud stage, and a change in the ratio of nuclear size to cell size was observed shortly after zygotic genome activation (ZGA), suggesting that differential gene expression contributes to size differences. Transcriptome analysis at the onset of ZGA identified twelve transcription factors paternally expressed in hybrids. A screen of these X. tropicalis factors by expression in X. laevis embryos revealed that Hes7 and Ventx2 significantly reduced X. laevis body length size by the tailbud stage, although nuclear to cell size scaling relationships were not affected as in the hybrid. Together, these results suggest that transcriptional regulation contributes to biological size control in Xenopus.

scholarly journals World–Views and the Epistemic Foundations of Theism

1989 ◽  
Vol 25 (1) ◽  
pp. 31-51 ◽  
Author(s):  
Joseph Runzo
Keyword(s):  
World View ◽  
Fundamental Question ◽  
World Views ◽  
Theistic Belief ◽  
Insight Into

Epistemological issues have inevitably been perennial issues for theism. For any claim to have insight into the nature and acts of the divine requires some sort of substantiation. And the appeal to faith typically made to meet this demand is often unconvincing. This raises a fundamental question: what could constitute proper grounds for theistic belief? In attempting to anwser this question, we will need to address the underlying epistemic issue of what justifies commitment to any world–view.

scholarly journals Investigation of the Impact of Cross-Polymerization on the Structural and Frictional Properties of Alkylsilane Monolayers Using Molecular Simulation

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 639 ◽  
Author(s):  
Jana E. Black ◽  
Andrew Z. Summers ◽  
Christopher R. Iacovella ◽  
Peter T. Cummings ◽  
Clare McCabe
Keyword(s):  
Amorphous Silica ◽  
Molecular Level ◽  
Level Structure ◽  
Fundamental Question ◽  
Silica Surfaces ◽  
Frictional Properties ◽  
Frictional Performance ◽  
The Impact ◽  
First Time ◽  
Insight Into

Cross-linked chemisorbed n-alkylsilane (CH3(CH2)n−1Si(OH)3) monolayers on amorphous silica surfaces have been studied and their structural properties and frictional performance were compared to those of equivalent monolayers without cross-linkages. The simulations isolated for the first time the effects of both siloxane cross-linkages and the fraction of chains chemisorbed to the surface, providing insight into a longstanding fundamental question in the literature regarding molecular-level structure. The results demonstrate that both cross-linkages and the fraction of chemisorbed chains affect monolayer structure in small but measurable ways, particularly for monolayers constructed from short chains; however, these changes do not appear to have a significant impact on frictional performance.

scholarly journals How prolonged expression of Hunchback, a temporal transcription factor, re-wires locomotor circuits

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Julia L Meng ◽  
Zarion D Marshall ◽  
Meike Lobb-Rabe ◽  
Ellie S Heckscher
Keyword(s):  
Stem Cells ◽  
Transcription Factor ◽  
Stem Cell ◽  
Motor Neurons ◽  
Fundamental Question ◽  
Dendrite Morphology ◽  
Neuronal Stem Cells ◽  
Molecular Information ◽  
The Relationship ◽  
Insight Into

How circuits assemble starting from stem cells is a fundamental question in developmental neurobiology. We test the hypothesis that, in neuronal stem cells, temporal transcription factors predictably control neuronal terminal features and circuit assembly. Using the Drosophila motor system, we manipulate expression of the classic temporal transcription factor Hunchback (Hb) specifically in the NB7-1 stem cell, which produces U motor neurons (MNs), and then we monitor dendrite morphology and neuromuscular synaptic partnerships. We find that prolonged expression of Hb leads to transient specification of U MN identity, and that embryonic molecular markers do not accurately predict U MN terminal features. Nonetheless, our data show Hb acts as a potent regulator of neuromuscular wiring decisions. These data introduce important refinements to current models, show that molecular information acts early in neurogenesis as a switch to control motor circuit wiring, and provide novel insight into the relationship between stem cell and circuit.

Calibration problems in hydrogen luminosities

1966 ◽  
Vol 24 ◽  
pp. 322-330
Author(s):  
A. Beer
Keyword(s):  
Galactic Structure ◽  
B Stars ◽  
Insight Into

The investigations which I should like to summarize in this paper concern recent photo-electric luminosity determinations of O and B stars. Their final aim has been the derivation of new stellar distances, and some insight into certain patterns of galactic structure.

Stochasting modeling of planetary ring systems

1984 ◽  
Vol 75 ◽  
pp. 461-469 ◽  
Author(s):  
Robert W. Hart
Keyword(s):  
Maximum Entropy ◽  
Ring System ◽  
The Sun ◽  
Ultimate State ◽  
Interparticle Interactions ◽  
Ring Systems ◽  
First Order ◽  
Planetary Ring ◽  
Insight Into

ABSTRACTThis paper models maximum entropy configurations of idealized gravitational ring systems. Such configurations are of interest because systems generally evolve toward an ultimate state of maximum randomness. For simplicity, attention is confined to ultimate states for which interparticle interactions are no longer of first order importance. The planets, in their orbits about the sun, are one example of such a ring system. The extent to which the present approximation yields insight into ring systems such as Saturn's is explored briefly.

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

Structure and function of neural networks in the retina

1988 ◽  
Vol 46 ◽  
pp. 26-27
Author(s):  
Peter Sterling
Keyword(s):  
Ganglion Cells ◽  
Three Dimensional ◽  
Structure And Function ◽  
Synaptic Connections ◽  
Visual Axis ◽  
One Dimensional ◽  
Cat Retina ◽  
Ultrathin Sections ◽  
And Function ◽  
Insight Into

The synaptic connections in cat retina that link photoreceptors to ganglion cells have been analyzed quantitatively. Our approach has been to prepare serial, ultrathin sections and photograph en montage at low magnification (˜2000X) in the electron microscope. Six series, 100-300 sections long, have been prepared over the last decade. They derive from different cats but always from the same region of retina, about one degree from the center of the visual axis. The material has been analyzed by reconstructing adjacent neurons in each array and then identifying systematically the synaptic connections between arrays. Most reconstructions were done manually by tracing the outlines of processes in successive sections onto acetate sheets aligned on a cartoonist's jig. The tracings were then digitized, stacked by computer, and printed with the hidden lines removed. The results have provided rather than the usual one-dimensional account of pathways, a three-dimensional account of circuits. From this has emerged insight into the functional architecture.

Radiation Damage Studies with the HVEM

1972 ◽  
Vol 30 ◽  
pp. 680-681
Author(s):  
J. J. Laidler ◽  
B. Mastel
Keyword(s):  
Radiation Damage ◽  
Stainless Steels ◽  
Volume Expansion ◽  
Austenitic Stainless Steels ◽  
Test Facility ◽  
Fast Breeder Reactors ◽  
Breeder Reactors ◽  
Under Construction ◽  
Development Laboratory ◽  
Insight Into

One of the major materials problems encountered in the development of fast breeder reactors for commercial power generation is the phenomenon of swelling in core structural components and fuel cladding. This volume expansion, which is due to the retention of lattice vacancies by agglomeration into large polyhedral clusters (voids), may amount to ten percent or greater at goal fluences in some austenitic stainless steels. From a design standpoint, this is an undesirable situation, and it is necessary to obtain experimental confirmation that such excessive volume expansion will not occur in materials selected for core applications in the Fast Flux Test Facility, the prototypic LMFBR now under construction at the Hanford Engineering Development Laboratory (HEDL). The HEDL JEM-1000 1 MeV electron microscope is being used to provide an insight into trends of radiation damage accumulation in stainless steels, since it is possible to produce atom displacements at an accelerated rate with 1 MeV electrons, while the specimen is under continuous observation.

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