On the siting of gases shock-emplaced from internal cavities in basalt

1988 ◽  
Vol 52 (12) ◽  
pp. 2775-2783 ◽  
Author(s):  
R.C Wiens
Keyword(s):  
Internal Cavities

scholarly journals Conjuring up a ghost: structural and functional characterization of FhuF, a ferric siderophore reductase from E. coli

2021 ◽  
Author(s):  
I. B. Trindade ◽  
G. Hernandez ◽  
E. Lebègue ◽  
F. Barrière ◽  
T. Cordeiro ◽  
...  
Keyword(s):  
Functional Characterization ◽  
Paramagnetic Nmr ◽  
E Coli ◽  
The Past ◽  
Internal Cavities ◽  
Structural Differences ◽  
Bond Strengths ◽  
Redox Bohr Effect ◽  
Micromolar Range

AbstractIron is a fundamental element for virtually all forms of life. Despite its abundance, its bioavailability is limited, and thus, microbes developed siderophores, small molecules, which are synthesized inside the cell and then released outside for iron scavenging. Once inside the cell, iron removal does not occur spontaneously, instead this process is mediated by siderophore-interacting proteins (SIP) and/or by ferric-siderophore reductases (FSR). In the past two decades, representatives of the SIP subfamily have been structurally and biochemically characterized; however, the same was not achieved for the FSR subfamily. Here, we initiate the structural and functional characterization of FhuF, the first and only FSR ever isolated. FhuF is a globular monomeric protein mainly composed by α-helices sheltering internal cavities in a fold resembling the “palm” domain found in siderophore biosynthetic enzymes. Paramagnetic NMR spectroscopy revealed that the core of the cluster has electronic properties in line with those of previously characterized 2Fe–2S ferredoxins and differences appear to be confined to the coordination of Fe(III) in the reduced protein. In particular, the two cysteines coordinating this iron appear to have substantially different bond strengths. In similarity with the proteins from the SIP subfamily, FhuF binds both the iron-loaded and the apo forms of ferrichrome in the micromolar range and cyclic voltammetry reveals the presence of redox-Bohr effect, which broadens the range of ferric-siderophore substrates that can be thermodynamically accessible for reduction. This study suggests that despite the structural differences between FSR and SIP proteins, mechanistic similarities exist between the two classes of proteins. Graphic abstract

The internal cavities of pike α-parvalbumin probably contain water

BIOPHYSICS ◽  
2012 ◽  
Vol 57 (3) ◽  
pp. 282-284
Author(s):  
V. M. Tishchenko
Keyword(s):  
Internal Cavities

Tolerance Specification and Related Issues for Additively Manufactured Products

2015 ◽  
Author(s):  
Gaurav Ameta ◽  
Paul Witherell ◽  
Shawn Moylan ◽  
Robert Lipman
Keyword(s):  
Free Form ◽  
Complex Geometries ◽  
Geometric Accuracy ◽  
Current State ◽  
Manufactured Products ◽  
Internal Cavities ◽  
Tolerance Specification ◽  
Functional Features ◽  
Traditional Manufacturing ◽  
Am Processes

Additive manufacturing (AM) has gained increased attention in the last decade as a versatile manufacturing process for customized products. AM processes can create complex free-form shapes, introducing features such as internal cavities and lattices. These complex geometries are either not feasible or very costly with traditional manufacturing processes. This creates new challenges in maintaining and communicating dimensional and geometric accuracy of parts produced. In order to manufacture a product that meets functional needs, the specification of those needs through geometry, material and tolerances is necessary. This paper surveys the current state and needs of geometry related accuracy specification mechanisms for AM, including a review of specification standards such as ASME Y14.5 and ISO 1101. Emerging AM-related tolerancing challenges are identified, and a potential plan of action is put forth for addressing those challenges. Various issues highlighted in this paper are classified as (a) AM-driven specification issues and (b) specification issues highlighted by the versatility of AM processes. AM-driven specification issues include build direction, layer thickness, support structure related specification, and scan/track direction. Specification issues highlighted by the versatility of AM processes include, region-based tolerances for complex freeform surfaces, tolerancing internal functional features, tolerancing lattice and infills. Basic methods of solving these specification issues are also highlighted.

scholarly journals Materials Precursor Score: Modelling Chemists' Intuition for the Synthetic Accessibility of Porous Organic Cages

2021 ◽  
Author(s):  
Steven Bennett ◽  
Filip Szczypiński ◽  
Lukas Turcani ◽  
Michael Briggs ◽  
Rebecca L. Greenaway ◽  
...  
Keyword(s):  
Organic Molecules ◽  
Class Imbalance ◽  
Computational Prediction ◽  
Material Development ◽  
Computational Screening ◽  
Machine Learning Model ◽  
Synthetic Accessibility ◽  
Internal Cavities ◽  
Computational Discovery ◽  
Novel Structures

<div>Computation is increasingly being used to try to accelerate the discovery of new materials. One specific example of this is porous molecular materials, specifically porous organic cages, where the porosity of the materials predominantly comes from the internal cavities of the molecules themselves. The computational discovery of novel structures with useful properties is currently hindered by the difficulty in transitioning from a computational prediction to synthetic realisation. Attempts at experimental validation are often time-consuming, expensive and, frequently, the key bottleneck of material discovery. In this work, we developed a computational screening workflow for porous molecules that includes consideration of the synthetic difficulty of material precursors, aimed at easing the transition between computational prediction and experimental realisation. We trained a machine learning model by first collecting data on 12,553 molecules categorised either as `easy-to-synthesise' or `difficult-to-synthesise' by expert chemists with years of experience in organic synthesis. We used an approach to address the class imbalance present in our dataset, producing a binary classifier able to categorise easy-to-synthesise molecules with few false positives. We then used our model during computational screening for porous organic molecules to bias towards precursors whose easier synthesis requirements would make them promising candidates for experimental realisation and material development. We found that even by limiting precursors to those that are easier-to-synthesise, we are still able to identify cages with favourable, and even some rare, properties. </div>

The effect of protein internal cavities on ligand migration and binding in myoglobin

Micron ◽  
2004 ◽  
Vol 35 (1-2) ◽  
pp. 67-69 ◽  
Author(s):  
Karin Nienhaus ◽  
Gerd U Nienhaus
Keyword(s):  
Internal Cavities ◽  
Ligand Migration

scholarly journals The crystal structure of wild-type human brain neuroglobin reveals flexibility of the disulfide bond that regulates oxygen affinity

2014 ◽  
Vol 70 (4) ◽  
pp. 1005-1014 ◽  
Author(s):  
Beatriz G. Guimarães ◽  
Djemel Hamdane ◽  
Christophe Lechauve ◽  
Michael C. Marden ◽  
Béatrice Golinelli-Pimpaneau
Keyword(s):  
Disulfide Bond ◽  
Conformational Transition ◽  
Bond Formation ◽  
Oxygen Affinity ◽  
Disulfide Bridge ◽  
Wild Type ◽  
X Ray ◽  
Intramolecular Disulfide Bond ◽  
Internal Cavities ◽  
High Oxygen Affinity

Neuroglobin plays an important function in the supply of oxygen in nervous tissues. In human neuroglobin, a cysteine at position 46 in the loop connecting the C and D helices of the globin fold is presumed to form an intramolecular disulfide bond with Cys55. Rupture of this disulfide bridge stabilizes bi-histidyl haem hexacoordination, causing an overall decrease in the affinity for oxygen. Here, the first X-ray structure of wild-type human neuroglobin is reported at 1.74 Å resolution. This structure provides a direct observation of two distinct conformations of the CD region containing the intramolecular disulfide link and highlights internal cavities that could be involved in ligand migration and/or are necessary to enable the conformational transition between the low and high oxygen-affinity states following S—S bond formation.

Research of plastic ice, mineral formations and air of multi-frozen karst cave Heetey in Transbaikalia

2020 ◽  
Vol 26 (7) ◽  
pp. 33-43
Author(s):  
I. Zheleznyak ◽  
◽  
S. Tsyrenzhapov ◽  
А. Gurulev ◽  
◽  
...  
Keyword(s):  
Radon Concentration ◽  
Maximum Level ◽  
Natural Environments ◽  
Geochemical Background ◽  
Karst Cave ◽  
Ice Volume ◽  
Internal Cavities ◽  
The Subject ◽  
Microwave Radiometers ◽  
Physical And Chemical

Heetey caves (“cold” and “warm”) which are located in the southern part of the permafrost in the Transbaikal Region have been chosen as the object of the research in the article. The subject is the physical and chemical parameters of the object. The results of the research in the “cold” Heetey cave are given in more detail. The following methods of this object research were chosen: study of the chemical composition of cave air using a chromatograph; radar survey of the cave grotto in the centimeter range; measurement of its own radio-thermal radiation using microwave radiometers. As a result of the research, the following results were obtained. The article provides information on the natural conditions that determine the dependence of the state of natural environments in the Heetey karst caves. The characteristics of occurrence and composition conditions of the natural environments of a karst cave (geological, cryogenic, atmospheric, groundwater) are given, taking into account the cryogenesis of their formation, transformation and influence on the cave air composition. A description of a rare low-temperature mineral, aragonite, which was first discovered in the cave and which is transformed into calcite over time is described. It is shown that the ice cover at the bottom of the cave has a layered structure, which is due to the seasonal ingress of surface water into the cave. The results of measurements of the surface air composition above the rocks’ surface and in caves, namely the content of oxygen, nitrogen, carbon dioxide, explosive gases – methane and hydrogen, mercury vapors are presented. A previously unknown fact of an increased geochemical background of radon concentration has been established. The most probable reasons for the formation and increased background of radon concentration are indicated. Microwave radiometric measurements have shown that there has been warming inside the cave over the past decade. This fact is associated with a general warming of the climate in Transbaikalia, as well as with an increase in the number of visits to caves by unorganized tourists. With the use of a 10 GHz nanosecond radar, hidden internal cavities were discovered in the roof of the cave, which can further lead to its destruction. The prints on the walls of the cave (in its lower part) show that the level of the ice sheet in 2015 is lower than its maximum level (1990) by 10 cm, which corresponds to a loss of ice volume of 12...15 m3 per year

scholarly journals A processing center for using digital hybrid technologies

2018 ◽  
Vol 44 ◽  
pp. 00059 ◽  
Author(s):  
Dmitry Masailo ◽  
Alexey Orlov ◽  
Vadim Sufiyarov ◽  
Andrey Volkov
Keyword(s):  
Machine Tool ◽  
Industry 4.0 ◽  
Industrial Development ◽  
Industrial Robot ◽  
Additive Technologies ◽  
Digital Manufacturing ◽  
Functionally Gradient ◽  
Internal Cavities ◽  
Hybrid Technologies

The role of additive technologies in industrial development was highlighted, in particular, for implementation of the concept “Industry 4.0”. We discussed their significance for digital manufacturing of parts having complex configuration with internal cavities and functionally gradient properties. We analyzed the main drawbacks of additive technologies and suggested the ways to overcome them. We described the problem in creating the equipment for hybrid technologies on the basis of a processing center and an industrial robot. We developed a concept for creating a Russian-made machine-tool for using hybrid technologies. Solutions are proposed for improving the structure of the material of parts.

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