Structural Complexity in a Lizard Communication System: The Sceloporus graciosus "Push-Up" Display

Copeia ◽  
1994 ◽  
Vol 1994 (4) ◽  
pp. 944 ◽  
Author(s):  
Emília P. Martins ◽  
Emilia P. Martins
Keyword(s):  
Communication System ◽  
Structural Complexity ◽  
Sceloporus Graciosus ◽  
Push Up

Conformation of eukaryotic ribosomal RNAs

1983 ◽  
Vol 41 ◽  
pp. 592-593
Author(s):  
M. Boublik ◽  
G. Thornton ◽  
G. Oostergetel ◽  
J.F. Hainfeld ◽  
J.S. Wall
Keyword(s):  
Molecular Weight ◽  
Mass Measurement ◽  
Carbon Film ◽  
Structural Complexity ◽  
Scanning Transmission Electron Microscope ◽  
Electron Microscopic ◽  
Pure Nitrogen ◽  
Freeze Dried ◽  
Scanning Transmission ◽  
Partially Unfolded

Understanding the structural complexity of ribosomes and their role in protein synthesis requires knowledge of the conformation of their components - rRNAs and proteins. Application of dedicated scanning transmission electron microscope (STEM), electrical discharge of the support carbon film in an atmosphere of pure nitrogen, and determination of the molecular weight of individual rRNAs enabled us to obtain high resolution electron microscopic images of unstained freeze-dried rRNA molecules from BHK cells in a form suitable for evaluation of their 3-D structure. Preliminary values for the molecular weight of 28S RNA from the large and 18S RNA from the small ribosomal subunits as obtained by mass measurement were 1.84 x 106 and 0.97 x 106, respectively. Conformation of rRNAs consists, in general, of alternating segments of intramolecular hairpin stems and single stranded loops in a proportion which depends on their ionic environment, the Mg++ concentration in particular. Molecules of 28S RNA (Fig. 1) and 18S RNA (not shown) obtained by freeze-drying from a solution of 60 mM NH+4 acetate and 2 mM Mg++ acetate, pH 7, appear as partially unfolded coils with compact cores suggesting a high degree of ordered secondary structure.

Observations of Frozen-Hydrated Microtubules

1990 ◽  
Vol 48 (1) ◽  
pp. 504-505
Author(s):  
D. Chrétien ◽  
D. Job ◽  
R.H. Wade
Keyword(s):  
Fourier Transforms ◽  
Structural Complexity ◽  
Image Contrast ◽  
Phase Behaviour ◽  
Experimental Conditions ◽  
Thin Sections ◽  
Surface Lattice ◽  
Cilia And Flagella ◽  
Outstanding Question

Microtubules are filamentary structures found in the cytoplasm of eukaryotic cells, where, together with actin and intermediate filaments, they form the components of the cytoskeleton. They have many functions and show various levels of structural complexity as witnessed by the singlet, doublet and triplet structures involved in the architecture of centrioles, basal bodies, cilia and flagella. The accepted microtubule model consists of a 25 nm diameter hollow tube with a wall made up of 13 paraxial protofilaments (pf). Each pf is a string of aligned tubulin dimers. Some results have suggested that the pfs follow a superhelix. To understand how microtubules function in the cell an accurate model of the surface lattice is one of the requirements. For example the 9x2 architecture of the axoneme will depend on the organisation of its component microtubules. We should also note that microtubules with different numbers of pfs have been observed in thin sections of cellular and of in-vitro material. An outstanding question is how does the surface lattice adjust to these different pf numbers?We have been using cryo-electron microscopy of frozen-hydrated samples to study in-vitro assembled microtubules. The experimental conditions are described in detail in this reference. The results obtained in conjunction with thin sections of similar specimens and with axoneme outer doublet fragments have already allowed us to characterise the image contrast of 13, 14 and 15 pf microtubules on the basis of the measured image widths, of the the image contrast symmetry and of the amplitude and phase behaviour along the equator in the computed Fourier transforms. The contrast variations along individual microtubule images can be interpreted in terms of the geometry of the microtubule surface lattice. We can extend these results and make some reasonable predictions about the probable surface lattices in the case of other pf numbers, see Table 1. Figure 1 shows observed images with which these predictions can be compared.

Structural Aspects of Phonological Development

1988 ◽  
Vol 19 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Karen E. Pollock ◽  
Richard G. Schwartz
Keyword(s):  
Clinical Management ◽  
Structural Complexity ◽  
Strong Preference ◽  
Phonological Development ◽  
Structural Position ◽  
Phonological Disorders ◽  
Syllabic Structure ◽  
The Relationship ◽  
Structural Aspects ◽  
Target Words

The relationship between syllabic structure and segmental development was examined longitudinally in a child with a severe phonological disorder. Six speech samples were collected over a 4-year period (3:5 to 7:3). Analyses revealed gradual increases in the complexity and diversity of the syllable structures produced, and positional preferences for sounds within these forms. With a strong preference for [d] and [n] at the beginning of syllables, other consonants appeared first at the end of syllables. Implications for clinical management of phonological disorders include the need to consider both structural position and structural complexity in assessing segmental skills and in choosing target words for intervention.

AAC Decision-Making and Mobile Technology: Points to Ponder

2014 ◽  
Vol 23 (2) ◽  
pp. 104-111 ◽  
Author(s):  
Mary Ann Abbott ◽  
Debby McBride
Keyword(s):  
Decision Making ◽  
Mobile Technology ◽  
Communication System ◽  
Augmentative And Alternative Communication ◽  
Evaluation Process ◽  
Decision Making Process ◽  
Alternative Communication ◽  
Ipod Touch ◽  
Feature Match

The purpose of this article is to outline a decision-making process and highlight which portions of the augmentative and alternative communication (AAC) evaluation process deserve special attention when deciding which features are required for a communication system in order to provide optimal benefit for the user. The clinician then will be able to use a feature-match approach as part of the decision-making process to determine whether mobile technology or a dedicated device is the best choice for communication. The term mobile technology will be used to describe off-the-shelf, commercially available, tablet-style devices like an iPhone®, iPod Touch®, iPad®, and Android® or Windows® tablet.

A Community Based High Risk Register for Hearing Loss

1982 ◽  
Vol 47 (4) ◽  
pp. 373-375 ◽  
Author(s):  
James L. Fitch ◽  
Thomas F. Williams ◽  
Josephine E. Etienne
Keyword(s):  
Hearing Loss ◽  
System Identification ◽  
High Risk ◽  
Language Learning ◽  
Education Program ◽  
Communication System ◽  
Auditory Signal ◽  
Early Age ◽  
Community Based ◽  
Children With Hearing Loss

The critical need to identify children with hearing loss and provide treatment at the earliest possible age has become increasingly apparent in recent years (Northern & Downs, 1978). Reduction of the auditory signal during the critical language-learning period can severely limit the child's potential for developing a complete, effective communication system. Identification and treatment of children having handicapping conditions at an early age has gained impetus through the Handicapped Children's Early Education Program (HCEEP) projects funded by the Bureau of Education for the Handicapped (BEH).

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