Framboid Mineralogy

2021 ◽  
pp. 153-168
Author(s):  
David Rickard
Keyword(s):  
Detailed Examination ◽  
Crystal Habit ◽  
Limiting Factors ◽  
Iron Sulfate ◽  
Pyrite Framboids ◽  
Framboid Formation ◽  
Crystalline Aggregates ◽  
Constituent Elements ◽  
Microcrystalline Material

Framboids are dominantly made of pyrite. The limiting factors for other minerals forming framboids include the requirements of crystal habit, solubility, and natural abundances of the constituent elements for framboid formation. Detailed examination of reports of non-pyritic framboids reveal microcrystalline material within and associated with framboids (e.g., greigite) and sub-spherical crystalline aggregates (e.g., marcasite, chalcocite-digenite, magnetite). Framboids are sometimes observed replaced by other minerals. Pyrite framboids are often formed during the earliest stages of sedimentation or mineralization and therefore are subject to further reactions with later fluids. Minerals such as copper, cobalt, zinc, and lead sulfides often display framboidal forms that have replaced original pyrite framboids. Likewise, oxidation of pyrite under some conditions can produce iron (oxyhydr)oxide and iron sulfate framboids.

Electron Irradiation Effects in Polyoxymethylene Crystals Grown Inside Trioxane Crystals

1971 ◽  
Vol 29 ◽  
pp. 78-79
Author(s):  
J. P. Colson ◽  
D. H. Reneker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Detailed Examination ◽  
The Other ◽  
Electron Micrograph ◽  
Irradiation Effects ◽  
Threefold Axis ◽  
Typical Sample ◽  
Polymer Crystals ◽  
Chain Axis

Polyoxymethylene (POM) crystals grow inside trioxane crystals which have been irradiated and heated to a temperature slightly below their melting point. Figure 1 shows a low magnification electron micrograph of a group of such POM crystals. Detailed examination at higher magnification showed that three distinct types of POM crystals grew in a typical sample. The three types of POM crystals were distinguished by the direction that the polymer chain axis in each crystal made with respect to the threefold axis of the trioxane crystal. These polyoxymethylene crystals were described previously.At low magnifications the three types of polymer crystals appeared as slender rods. One type had a hexagonal cross section and the other two types had rectangular cross sections, that is, they were ribbonlike.

A new dissociation mode for dislocations in silicon

1978 ◽  
Vol 36 (1) ◽  
pp. 346-347
Author(s):  
A. Ourmazd ◽  
G.R. Booker ◽  
C.J. Humphreys
Keyword(s):  
Detailed Examination ◽  
Experimental Results ◽  
Dislocation Network ◽  
Weak Beam ◽  
Phosphorus Doped

A (111) phosphorus-doped Si specimen, thinned to give a TEM foil of thickness ∼ 150nm, contained a dislocation network lying on the (111) plane. The dislocation lines were along the three <211> directions and their total Burgers vectors,ḇt, were of the type , each dislocation being of edge character. TEM examination under proper weak-beam conditions seemed initially to show the standard contrast behaviour for such dislocations, indicating some dislocation segments were undissociated (contrast A), while other segments were dissociated to give two Shockley partials separated by approximately 6nm (contrast B) . A more detailed examination, however, revealed that some segments exhibited a third and anomalous contrast behaviour (contrast C), interpreted here as being due to a new dissociation not previously reported. Experimental results obtained for a dislocation along [211] with for the six <220> type reflections using (g,5g) weak-beam conditions are summarised in the table below, together with the relevant values.

Effects of sterilization modes on the mechanical strengths of plaster of paris implants

1989 ◽  
Vol 47 ◽  
pp. 890-891
Author(s):  
K. Cowden ◽  
B. Giammara ◽  
T. Devine ◽  
J. Hanker
Keyword(s):  
Gamma Radiation ◽  
Calcium Sulfate ◽  
Significant Loss ◽  
Potassium Sulfate ◽  
Limiting Factors ◽  
Radiation Sterilization ◽  
Plaster Of Paris ◽  
Hardness Tester ◽  
Dry Heat ◽  
Calcium Sulfate Hemihydrate

Plaster of Paris (calcium sulfate hemihydrate, CaSO4. ½ H2O) has been used as a biomedical implant material since 1892. One of the primary limiting factors of these implants is their mechanical properties. These materials have low compressive and tensile strengths when compared to normal bone. These are important limiting factors where large biomechanical forces exist. Previous work has suggested that sterilization techniques could affect the implant’s strength. A study of plaster of Paris implant mechanical and physical properties to find optimum sterilization techniques therefore, could lead to a significant increase in their application and promise for future use as hard tissue prosthetic materials.USG Medical Grade Calcium Sulfate Hemihydrate Types A, A-1 and B, were sterilized by dry heat and by gamma radiation. Types A and B were additionally sterilized with and without the setting agent potassium sulfate (K2SO4). The plaster mixtures were then moistened with a minimum amount of water and formed into disks (.339 in. diameter x .053 in. deep) in polyethylene molds with a microspatula. After drying, the disks were fractured with a Stokes Hardness Tester. The compressive strengths of the disks were obtained directly from the hardness tester. Values for the maximum tensile strengths σo were then calculated: where (P = applied compression, D = disk diameter, and t = disk thickness). Plaster disks (types A and B) that contained no setting agent showed a significant loss in strength with either dry heat or gamma radiation sterilization. Those that contained potassium sulfate (K2SO4) did not show a significant loss in strength with either sterilization technique. In all comparisons (with and without K2SO4 and with either dry heat or gamma radiation sterilization) the type B plaster had higher compressive and tensile strengths than that of the type A plaster. The type A-1 plaster however, which is specially modified for accelerated setting, was comparable to that of type B with K2SO4 in both compressive and tensile strength (Table 1).

Mosaic Mapping: A Means of Tiling Images to Shorten Acquisition Speed for Lower - Magnification SEM Images and Wavelength Dispersive Spectrometers (WDS) X-Ray Maps

1996 ◽  
Vol 54 ◽  
pp. 438-439
Author(s):  
J.D. Geller ◽  
C.R. Herrington
Keyword(s):  
Limiting Factors ◽  
X Rays ◽  
Angular Range ◽  
Acceptance Angle ◽  
Sem Images ◽  
Worst Case ◽  
X Ray ◽  
Focusing Distance ◽  
Layered Crystals ◽  
Working Distance

The minimum magnification for which an image can be acquired is determined by the design and implementation of the electron optical column and the scanning and display electronics. It is also a function of the working distance and, possibly, the accelerating voltage. For secondary and backscattered electron images there are usually no other limiting factors. However, for x-ray maps there are further considerations. The energy-dispersive x-ray spectrometers (EDS) have a much larger solid angle of detection that for WDS. They also do not suffer from Bragg’s Law focusing effects which limit the angular range and focusing distance from the diffracting crystal. In practical terms EDS maps can be acquired at the lowest magnification of the SEM, assuming the collimator does not cutoff the x-ray signal. For WDS the focusing properties of the crystal limits the angular range of acceptance of the incident x-radiation. The range is dependent upon the 2d spacing of the crystal, with the acceptance angle increasing with 2d spacing. The natural line width of the x-ray also plays a role. For the metal layered crystals used to diffract soft x-rays, such as Be - O, the minimum magnification is approximately 100X. In the worst case, for the LEF crystal which diffracts Ti - Zn, ˜1000X is the minimum.

Communication Sciences and Disorders PhD Graduates' Perceptions of Their PhD Program

2020 ◽  
Vol 5 (2) ◽  
pp. 463-478
Author(s):  
Elizabeth Crais ◽  
Melody Harrison Savage
Keyword(s):  
Detailed Examination ◽  
Career Expectations ◽  
Doctoral Preparation ◽  
Creative Solutions ◽  
Phd Education ◽  
Doctor Of Philosophy ◽  
First Time ◽  
Students Success ◽  
Phd Program

Purpose The shortage of doctor of philosophy (PhD)–level applicants to fill academic and research positions in communication sciences and disorders (CSD) programs calls for a detailed examination of current CSD PhD educational practices and the generation of creative solutions. The intended purposes of the article are to encourage CSD faculty to examine their own PhD program practices and consider the perspectives of recent CSD PhD graduates in determining the need for possible modifications. Method The article describes the results of a survey of 240 CSD PhD graduates and their perceptions of the challenges and facilitators to completing a PhD degree; the quality of their preparation in research, teaching, and job readiness; and ways to improve PhD education. Results Two primary themes emerged from the data highlighting the need for “matchmaking.” The first time point of needed matchmaking is prior to entry among students, mentors, and expectations as well as between aspects of the program that can lead to students' success and graduation. The second important matchmaking need is between the actual PhD preparation and the realities of the graduates' career expectations, and those placed on graduates by their employers. Conclusions Within both themes, graduate's perspectives and suggestions to help guide future doctoral preparation are highlighted. The graduates' recommendations could be used by CSD PhD program faculty to enhance the quality of their program and the likelihood of student success and completion. Supplemental Material https://doi.org/10.23641/asha.11991480

Apparitions of ‘Freedom’ (the Word)

Derrida Today ◽  
2012 ◽  
Vol 5 (1) ◽  
pp. 39-54 ◽  
Author(s):  
Marian Hobson
Keyword(s):  
Detailed Examination ◽  
Close Attention ◽  
Change Of Perspective

Derrida thematises his writing through a change of perspective which moves from very detailed examination of an argument to more general statements. This paper is a consideration of how Derrida anchors his close attention to the detail of an argument in a wider philosophical-historical and indeed social framework. In this paper, the word in question is ‘freedom’, discussed with the philosopher and psychoanalyst Elisabeth Roudinesco; this paper moves back chronologically to Force of Law, and finally to a passage in Of Grammatology to demonstrate that in Derrida's work from early to late there is a web of reflection about freedom.

Essays on Hume, Smith and the Scottish Enlightenment

2018 ◽  
Author(s):  
Christopher J. Berry
Keyword(s):  
Intellectual History ◽  
David Hume ◽  
Adam Smith ◽  
Detailed Examination ◽  
Scottish Enlightenment ◽  
Subsequent Work ◽  
Retrospective Assessment ◽  
The 1960S

A collection of essays by a leading scholar. The work selected spans several decades, which together with three new unpublished pieces, cumulatively constitute a distinct interpretation of the Scottish Enlightenment as a whole while incorporating detailed examination of the work of David Hume and Adam Smith. There is, in addition, a substantial introduction which, alongside Berry’s personal intellectual history, provides a commentary on the development of the study of the Scottish Enlightenment from the 1960s. Each of the previously published chapters includes a postscript where Berry comments on subsequent work and his own retrospective assessment. The recurrent themes are the ideas of sociability and socialisation, the Humean science of man and Smith’s analysis of the relation between commerce and morality.

The innovative space as the most important element of theregional socio-economic space

2019 ◽  
pp. 60-70
Author(s):  
Larysa Gromozdova ◽  
Inna Stenicheva
Keyword(s):  
Basic Element ◽  
Information Support ◽  
Space Region ◽  
Regional Innovation ◽  
Economic Space ◽  
Mechanisms Of Formation ◽  
Innovation Space ◽  
Space Mechanisms ◽  
Constituent Elements

Purpose of the article: to determine the essence of different elements ofsocio-economic space of the region. Construction of the structure and isolationof individual elements of socio-economic space as a multi-vector formation.This article highlights the essence and different approaches to defining theconcepts, structure and mechanisms of formation of economic and social spacesof the region, innovation space as a basic element of socio-economic space.Research Methods: The methodological basis of the research is the fundamentalprinciples of economic theory, regional economy, scientific views and approachesof foreign and domestic scientists. To achieve the purpose of the study, themethods used at the empirical and theoretical levels were used: axiomatic,abstract, system-structural analysis, analogies and comparisons, graphoanalytic,by which the characterization of the nature of the concepts of space, socioeconomic space, as well as innovation space region. Their general properties,structure and functions are described.The criteria of optimality and balancesof interests in the formation of different types of space in the region areconsidered. The classification of the regional space is proposed, and the networkconnections of the innovation space according to components and elements arerevealed, which allows to study deeply the social, economic and other problemsof development of the region.Scientific novelty: the classification of regionalspace by separate constituent elements is proposed. The concept of “innovationspace” was introduced into scientific circulation, the scheme of networkconnections of the innovation space with other elements of the regional socioeconomic space was developed. Conclusions and Prospects for Further Research:In today’s context, it is possible to significantly improve the economic stateof development of Ukrainian regions by using a scientifically sound andcomprehensive approach to defining and studying the concepts of socioeconomic and innovative space.In the further study it is necessary to considerin detail the mechanism of organizational activity of innovation space in theregion. It is very important to pay attention to information support for theformation of the innovation space, the creation of a regional legal field ofinnovation space, mechanisms for coordinating regional innovation activitieswithin the innovation space, as well as the influence of internal and externalfactors on the formation and development of the innovation space.

PERSPECTIVE DEVELOPMENT OF WORLD PRODUCTION OF FEEDS FOR AQUACULTURE: ALTERNATIVE SOURCES OF RAW MATERIALS

2017 ◽  
pp. 67-78
Author(s):  
Lina Yurievna Lagutkina
Keyword(s):  
Raw Materials ◽  
Limiting Factors ◽  
Current Status ◽  
Feed Production ◽  
The World ◽  
Market Trends ◽  
Alternative Sources ◽  
World Industry ◽  
First Time ◽  
A Current

The author of the article discloses the prospects of development of the world feed production for aquaculture based on the analysis of key innovative technological and market trends. The author specifies that shortage, high cost, low ecological compatibility of traditional raw materials - fish flour - are among major limiting factors in the development of production of feeds for aquaculture. This fact, in turn, limits sustainable development of aquaculture both in Russia, and in the world in general. The article presents the overview of a current status of the world industry of feed production in aquaculture, where the regional situation is studied, as well. For the first time, there is given the outlook of innovative technologies in feed production based on the alternative sources of protein (on the example of projects of leading aquabiotechnological companies) which will determine industry’s objectives for the mid-term perspective.

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