Skeletal element independence and implications for quantification

2021 ◽  
Vol 35 ◽  
pp. 102796
Author(s):  
Valerie Sgheiza
Keyword(s):  
Skeletal Element

scholarly journals Generating Cluster Formulas Using The Primary Clusters And The K(n) Parameters

2018 ◽  
Vol 10 (2) ◽  
pp. 85
Author(s):  
Enos Masheija Rwantale Kiremire
Keyword(s):  
Transition Metal ◽  
Metal Clusters ◽  
Graphical Representations ◽  
Skeletal Element ◽  
Transition Metal Clusters ◽  
Primary Cluster

The formulas of transition metal clusters can be regarded as multiples of their respective PRIMARY CLUSTERS  and K(n) parameters. A primary cluster of a transition metal skeletal element can be defined as that  cluster of a mono-skeletal element which obeys the 18 electron rule. Such clusters, among others include, Cr(CO)6, Fe(CO)5, Ni(CO)4, and Zn(CO)3 and the respective K values of the skeletal elements are 6, 5, 4 and 3. The selected K(n) series are given and the derived hypothetical golden clusters are given as examples for illustrations. Selected known golden clusters are also found to be multiples of K(n) parameters and the 18 valence fragment cluster, AuL3.5. The graphical representations of a few selected examples of golden clusters are given.

scholarly journals Categorization of Boranes Into Clan Series

2020 ◽  
Vol 12 (1) ◽  
pp. 107
Author(s):  
Enos Masheija Rwantale Kiremire ◽  
Ivan Lule
Keyword(s):  
Skeletal Element ◽  
Cluster Number ◽  
Inherent Characteristic ◽  
Valence Electrons ◽  
Whole Number ◽  
Fundamental Equations ◽  
Isomeric Structures ◽  
Cluster Series

Boranes, despite their instability in nature, can be regarded as hydrocarbon relatives since a [BH] fragment corresponds to a carbon [C] skeletal element in terms of the number of valence electrons. The borane formula which can be expressed as BnHm usually appears in such a way that when (n) is even, then (m) is even and when (n) is odd, (m) is odd as well. Through the study of cluster series, it appears that the cluster number K which represents skeletal linkages is usually a whole number. This inherent characteristic confers unique order within borane clusters with nodal connectivity of 5 and the polyhedral nature of the borane clusters. The orderliness of the borane clusters is reflected by the ease of their categorization into clan series and their readily constructed geometrical isomeric structures. The cluster valence electrons can easily be calculated using one of the six recently discovered fundamental equations.

Animal Bones from Caves to Cities: Reverse Utility Curves as Methodological Artifacts

1997 ◽  
Vol 62 (4) ◽  
pp. 698-711 ◽  
Author(s):  
Curtis W. Marean ◽  
Carol J. Frey
Keyword(s):  
Iron Age ◽  
Positive Relationship ◽  
Mechanistic Explanation ◽  
Long Bone ◽  
Element Abundance ◽  
Long Bones ◽  
Skeletal Element ◽  
Economic Decisions ◽  
Abundance Estimates ◽  
Animal Bones

Utility-based studies are attractive to zooarchaeologists because they afford the opportunity of investigating economic decisions relative to particular contexts. While a positive relationship between utility and skeletal element abundance is anticipated at residential sites, a reverse utility curve is most common. A popular mechanistic explanation argues that reverse utility curves result from density-mediated destruction of bone, suggesting that utility-based studies will rarely be successful as density-mediated destruction will overwhelm any skeletal element patterning created by differential transport. We show with archaeological and experimental/naturalistic taphonomic data that the mechanistic explanation is overstated. Fauna from Kobeh cave (a Mousterian site) and "Ain Dara (an Iron Age site) both show a reverse utility pattern when estimates of long bone abundance are based just on ends (the procedure followed at all sites that have shown a reverse utility pattern), and all bones are plotted together. When long bone abundance is estimated from the middle shaft portion, the reverse utility pattern collapses and a positive relationship arises. The ubiquity of the reverse utility curve derives in many cases from basing long bone abundance estimates on ends and scatter-plotting the abundance of long bones with non-long bones, thus restricting the analysis to the least dense most spongy bone portions. Long bone abundance estimates must include the middle shaft portion to attain accurate estimates of element abundance. Long bone abundance, when based on shaft portions, can be usefully compared to utility to investigate utility-based models of human behavior.

scholarly journals Concealed weapons: erectile claws in African frogs

2008 ◽  
Vol 4 (4) ◽  
pp. 355-357 ◽  
Author(s):  
David C Blackburn ◽  
James Hanken ◽  
Farish A Jenkins
Keyword(s):  
Connective Tissue ◽  
Resting State ◽  
Skeletal Element ◽  
Concealed Weapons ◽  
Ventral Skin

Vertebrate claws are used in a variety of important behaviours and are typically composed of a keratinous sheath overlying the terminal phalanx of a digit. Keratinous claws, however, are rare in living amphibians; their microstructure and other features indicate that they probably originated independently from those in amniotes. Here we show that certain African frogs have a different type of claw, used in defence, that is unique in design among living vertebrates and lacks a keratinous covering. These frogs have sectorial terminal phalanges on their hind feet that become functional by cutting through the skin. In the resting state, the phalanx is subdermal and attached to a distal bony nodule, a neomorphic skeletal element, via collagen-rich connective tissue. When erected, the claw breaks free from the nodule and pierces the ventral skin. The nodule, suspended by a sheath attached to the terminal phalanx and supported by collagenous connections to the dermis, remains fixed in place. While superficially resembling the shape of claws in other tetrapods, these are the only vertebrate claws known to pierce their way to functionality.

scholarly journals Sall4-Gli3 system in early limb progenitors is essential for the development of limb skeletal elements

2015 ◽  
Vol 112 (16) ◽  
pp. 5075-5080 ◽  
Author(s):  
Ryutaro Akiyama ◽  
Hiroko Kawakami ◽  
Julia Wong ◽  
Isao Oishi ◽  
Ryuichi Nishinakamura ◽  
...  
Keyword(s):  
Progenitor Cells ◽  
Sonic Hedgehog ◽  
Limb Development ◽  
Critical Role ◽  
Dependent Manner ◽  
Skeletal Element ◽  
Proximal Development ◽  
Limb Outgrowth ◽  
Common Regulator

Limb skeletal elements originate from the limb progenitor cells, which undergo expansion and patterning to develop each skeletal element. Posterior-distal skeletal elements, such as the ulna/fibula and posterior digits develop in a Sonic hedgehog (Shh)-dependent manner. However, it is poorly understood how anterior-proximal elements, such as the humerus/femur, the radius/tibia and the anterior digits, are developed. Here we show that the zinc finger factors Sall4 and Gli3 cooperate for proper development of the anterior-proximal skeletal elements and also function upstream of Shh-dependent posterior skeletal element development. Conditional inactivation of Sall4 in the mesoderm before limb outgrowth caused severe defects in the anterior-proximal skeletal elements in the hindlimb. We found that Gli3 expression is reduced in Sall4 mutant hindlimbs, but not in forelimbs. This reduction caused posteriorization of nascent hindlimb buds, which is correlated with a loss of anterior digits. In proximal development, Sall4 integrates Gli3 and the Plzf-Hox system, in addition to proliferative expansion of cells in the mesenchymal core of nascent hindlimb buds. Whereas forelimbs developed normally in Sall4 mutants, further genetic analysis identified that the Sall4-Gli3 system is a common regulator of the early limb progenitor cells in both forelimbs and hindlimbs. The Sall4-Gli3 system also functions upstream of the Shh-expressing ZPA and the Fgf8-expressing AER in fore- and hindlimbs. Therefore, our study identified a critical role of the Sall4-Gli3 system at the early steps of limb development for proper development of the appendicular skeletal elements.

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