Mechanized Proof of Type Preservation for Polymorphic Lambda Calculi Using Abella

2020 ◽  
Vol 47 (5) ◽  
pp. 496-503
Author(s):  
Ki Yung Ahn
Keyword(s):  
Type Preservation

scholarly journals Mechanism for Burgess Shale-type preservation

2012 ◽  
Vol 109 (14) ◽  
pp. 5180-5184 ◽  
Author(s):  
R. R. Gaines ◽  
E. U. Hammarlund ◽  
X. Hou ◽  
C. Qi ◽  
S. E. Gabbott ◽  
...  
Keyword(s):  
Burgess Shale ◽  
Type Preservation

Late Proterozoic–Early Phanerozoic ‘Taphonomic Windows’: The Environmental and Temporal Distribution of Recurrent Modes of Exceptional Preservation

2014 ◽  
Vol 20 ◽  
pp. 289-313
Author(s):  
Patrick J. Orr
Keyword(s):  
Evolutionary Biology ◽  
Intermediate Phase ◽  
Temporal Distribution ◽  
Exceptional Preservation ◽  
Global Environmental ◽  
History Of ◽  
Type Preservation ◽  
Late Neoproterozoic ◽  
Diagenetic History ◽  
Organic Remains

Exceptional biotas—those in which the non-biomineralized tissues of organisms are preserved—are an important record of the evolutionary biology of the late Neoproterozoic—early Phanerozoic interval. Most of these biotas exhibit one of four modes of preservation: preservation of either 1) internal and external detail (Doushantuo-type preservation) or, 2) external cuticles (Orsten-type preservation) in calcium phosphate; 3) coating in pyrite films and infills (Beecher's Bed-type preservation); and 4) preservation of organic remains (Burgess Shale-type preservation). The global environmental and temporal distribution of each mode of preservation is reasonably well constrained, but not why these taphonomic windows existed when they did. The late Neoproterozoic – early Phanerozoic interval is characterized by complex, interlinked, physical, geochemical and biological changes to the Earth's biosphere and geosphere. The changing ecology of marine environments (from matground to mixgrounds: the ‘Agronomic Revolution’) occurred via an intermediate phase of stiffened, but not microbially bound sediments that extended the interval over which exceptional preservation occurred. Prolonged eustatic sea-level rise across flat-lying continental platforms ensured environments conducive to exceptional preservation were developed and, critically, sustained over large contiguous areas. During this, regolith on continental surfaces was recycled, providing an integral source of sediment and ions relevant to mineral authigenesis. Superimposed on these broad-scale changes are specific drivers that controlled the duration of individual taphonomic windows; elucidating these requires a better understanding of the environmental context and diagenetic history of fossiliferous successions at the intra-basinal scale.

Exceptional Fossil Conservation through Phosphatization

2014 ◽  
Vol 20 ◽  
pp. 59-82 ◽  
Author(s):  
James D. Schiffbauer ◽  
Adam F. Wallace ◽  
Jesse Broce ◽  
Shuhai Xiao
Keyword(s):  
Calcium Phosphate ◽  
Soft Tissues ◽  
Geochemical Processes ◽  
Comprehensive Description ◽  
Animal Evolution ◽  
Pore Fluid Chemistry ◽  
Type Preservation ◽  
Fossil Preservation ◽  
Calcium Phosphate Precipitation ◽  
Taphonomic Processes

This paper addresses the taphonomic processes responsible for fossil preservation in calcium phosphate, or phosphatization. Aside from silicification and rarer examples of carbonaceous compression, phosphatization is the only taphonomic mode claimed to preserve putative subcellular structures. Because this fossilization window can record such valuable information, a comprehensive understanding of its patterns of occurrence and the geochemical processes involved in the replication of soft tissues are critical endeavors. Fossil phosphatization was most abundant during the latest Neoproterozoic through the early Paleozoic, coinciding with the decline of non-pelletal phosphorite deposits. Its temporal abundance during this timeframe makes it a particularly valuable window for the study of early animal evolution. Several occurrences of phosphatization from the Ediacaran through the Permian Period, including Doushantuo-type preservation of embryo-like fossils and acritarchs, phosphatized gut tracts within Burgess Shale-type carbonaceous compressions, Orsten-type preservation of meiofaunas, and other cases from the later Paleozoic are reviewed. In addition, a comprehensive description of the geochemical controls of calcium phosphate precipitation from seawater is provided, with a focus on the rates of phosphate nucleation and growth, favorable nucleation substrates, and properties of substrate tissue and pore-fluid chemistry. It is hoped that the paleontological and geochemical summaries provided here offer a practical and valuable guide to the Neoproterozoic–Paleozoic phosphatization window.

Photography-based taxonomy is still really inadequate, unnecessary, and potentially harmful for biological sciences. A reply to Thorpe (2017)

Bionomina ◽  
2017 ◽  
Vol 12 (1) ◽  
pp. 48-51
Author(s):  
VICTOR G.D. ORRICO
Keyword(s):  
Biological Sciences ◽  
Type A ◽  
Main Issue ◽  
Type Preservation ◽  
Definition Of

A recent defense of the photo-based taxonomy is discussed. The main issue concerns the simplistic definition of “type”. A comparison with other material forms of type preservation highlights weaknesses inherent to the use of photographs as types. Additional arguments from Thorpe’s contribution are also reviewed and disputed.

scholarly journals CPS transformation with affine types for call-by-value implicit polymorphism

2021 ◽  
Vol 5 (ICFP) ◽  
pp. 1-30
Author(s):  
Taro Sekiyama ◽  
Takeshi Tsukada
Keyword(s):  
Fundamental Property ◽  
The Other ◽  
Target Language ◽  
Logical Relation ◽  
Contextual Equivalence ◽  
Type Preservation ◽  
System F ◽  
Control Operators

Transformation of programs into continuation-passing style (CPS) reveals the notion of continuations, enabling many applications such as control operators and intermediate representations in compilers. Although type preservation makes CPS transformation more beneficial, achieving type-preserving CPS transformation for implicit polymorphism with call-by-value (CBV) semantics is known to be challenging. We identify the difficulty in the problem that we call scope intrusion. To address this problem, we propose a new CPS target language Λ open that supports two additional constructs for polymorphism: one only binds and the other only generalizes type variables. Unfortunately, their unrestricted use makes Λ open unsafe due to undesired generalization of type variables. We thus equip Λ open with affine types to allow only the type-safe generalization. We then define a CPS transformation from Curry-style CBV System F to type-safe Λ open and prove that the transformation is meaning and type preserving. We also study parametricity of Λ open as it is a fundamental property of polymorphic languages and plays a key role in applications of CPS transformation. To establish parametricity, we construct a parametric, step-indexed Kripke logical relation for Λ open and prove that it satisfies the Fundamental Property as well as soundness with respect to contextual equivalence.

Burgess Shale-type Preservation and its Distribution in Space and Time

2014 ◽  
Vol 20 ◽  
pp. 123-146 ◽  
Author(s):  
Robert R. Gaines
Keyword(s):  
Soft Tissues ◽  
Cambrian Explosion ◽  
Burgess Shale ◽  
Seawater Chemistry ◽  
Middle Cambrian ◽  
Space And Time ◽  
Fossil Assemblages ◽  
Type Preservation ◽  
Diagenetic Environment

Burgess Shale-type fossil assemblages provide a unique record of animal life in the immediate aftermath of the so-called “Cambrian explosion.” While most soft-bodied faunas in the rock record were conserved by mineral replication of soft tissues, Burgess Shale-type preservation involved the conservation of whole assemblages of soft-bodied animals as primary carbonaceous remains, often preserved in extraordinary anatomical detail. Burgess Shale-type preservation resulted from a combination of influences operating at both local and global scales that acted to drastically slow microbial degradation in the early burial environment, resulting in incomplete decomposition and the conservation of soft-bodied animals, many of which are otherwise unknown from the fossil record. While Burgess Shale-type fossil assemblages are primarily restricted to early and middle Cambrian strata (Series 2–3), their anomalous preservation is a pervasive phenomenon that occurs widely in mudstone successions deposited on multiple paleocontinents. Herein, circumstances that led to the preservation of Burgess Shale-type fossils in Cambrian strata worldwide are reviewed. A three-tiered rank classification of the more than 50 Burgess Shale-type deposits now known is proposed and is used to consider the hierarchy of controls that regulated the operation of Burgess Shale-type preservation in space and time, ultimately determining the total number of preserved taxa and the fidelity of preservation in each deposit. While Burgess Shale-type preservation is a unique taphonomic mode that ultimately was regulated by the influence of global seawater chemistry upon the early diagenetic environment, physical depositional (biostratinomic) controls are shown to have been critical in determining the total number of taxa preserved in fossil assemblages, and hence, in regulating many of the important differences among Burgess Shale-type deposits.

A Multicellular Alga with Exceptional Preservation from the Ediacaran of Nevada

2014 ◽  
Vol 88 (2) ◽  
pp. 263-268 ◽  
Author(s):  
Stephen M. Rowland ◽  
Margarita G. Rodriguez
Keyword(s):  
Spectral Analysis ◽  
New Species ◽  
Black Shale ◽  
Cellular Structure ◽  
New Genus ◽  
Single Specimen ◽  
Burgess Shale ◽  
Exceptional Preservation ◽  
First Occurrence ◽  
Type Preservation

Elainabella deepspringensis new genus new species is a one-mm-wide, non-biomineralized, three-dimensionally preserved fossil with segmented branches and apparent cellular structure. A single specimen was recovered from an interval of black shale within the Ediacaran portion of the Esmeralda Member of the Deep Spring Formation at Mt. Dunfee in Esmeralda County, Nevada. We interpret the fossil to be the thallus of a multicellular alga of uncertain division. EDS spectral analysis indicates that the exceptional preservation is not due to phosphatization or pyritization. Rather, it appears to be a case of Burgess Shale-type preservation, involving the kerogenization of non-mineralizing organisms. The fossil-bearing shale is closely associated with stromatolites, and we suggest that E. deepspringensis may have been an epibiont on stromatolites or other firm substrates. This is the first multicellular alga and the first occurrence of Burgess Shale-type preservation reported from the Ediacaran of Laurentia.

Sign in / Sign up

Export Citation Format

Share Document