TEM observation of cylindrite

1989 ◽  
Vol 47 ◽  
pp. 420-421
Author(s):  
Su Wang
Keyword(s):  
Long Range ◽  
Saed Pattern ◽  
The Past ◽  
Main Reflection ◽  
Different Types ◽  
Structural Modulation ◽  
The Common

Cylindrite, approximately FePb3Sn4Sb2S14, contains two different types of layers, pseudo-tetragonal(t-lattice) with PbS structure and pseudo-hexagonal (h-lattice) with SnS2 structure. The two kinds of layers are superimposed in the order of htht.., and the repeat periodicity is a. In the past only the composite SAED pattern corresponding to the b*c* plane of the two lattices was obtained as shown in Fig. 1a. Now we have succeeded, by careful tilting, in taking separate SAED patterns and HREM images of these two lattices(Figs. 2 and 3). The CBED pattern containing two [100] zone axes indicates: , as shown in Fig. lb.In the SAED patterns shown in Figs. 2, 3 and 4, each main reflection is accompanied by a row of satellite spots caused by the common structural modulation of the two lattices shown by the dark bands inthe HREM images. The rows of satellites, defined by q, in general donot parallel to any axes defined by the main reflections. In the q direction, the additional long-range periodicity corresponding to the satellites and the basic periodicity of both lattices are incommensurate.

Sociolinguistic typology and the uniformitarian hypothesis

2020 ◽  
pp. 44-57
Author(s):  
Peter Trudgill
Keyword(s):  
Social Factors ◽  
Historical Linguistics ◽  
Human Mind ◽  
Methodological Principle ◽  
Human Language ◽  
Language Faculty ◽  
The Past ◽  
Different Types ◽  
The Common ◽  
Linguistic Structures

One of the bases of historical linguistics is the uniformitarian principle: knowledge of processes that operated in the past can be inferred by observing ongoing processes in the present. This leads us to the methodological principle of using the present to explain the past. This chapter presents a sociolinguistic-typological perspective which investigates the extent to which it is possible to produce sociolinguistic explanations for linguistic structures. Insofar as the characteristics of individual languages are due to the nature of the human language faculty, there cannot be any questioning of the uniformitarian principle. But what if some of the characteristics of individual languages are due to social factors? Then the common faculty of the human mind will produce different types of structure in different societies at different moments in history. So the linguistic present might not altogether be like the linguistic past; and the methodology of using-the-present-to-explain-the-past could be less useful the further back in time we go.

scholarly journals Opsin-based photopigments expressed in the retina of a South American pit viper, Bothrops atrox (Viperidae)

2018 ◽  
Vol 35 ◽  
Author(s):  
Christiana Katti ◽  
Micaela Stacey-Solis ◽  
Nicole A. Coronel-Rojas ◽  
Wayne I.L. Davies
Keyword(s):  
Opsin Gene ◽  
South American ◽  
Long Wavelength ◽  
Rods And Cones ◽  
The Past ◽  
Different Types ◽  
The Common ◽  
Cone Opsins ◽  
General Studies ◽  
Bothrops Atrox

AbstractAlthough much is known about the visual system of vertebrates in general, studies regarding vision in reptiles, and snakes in particular, are scarce. Reptiles display diverse ocular structures, including different types of retinae such as pure cone, mostly rod, or duplex retinas (containing both rods and cones); however, the same five opsin-based photopigments are found in many of these animals. It is thought that ancestral snakes were nocturnal and/or fossorial, and, as such, they have lost two pigments, but retained three visual opsin classes. These are the RH1 gene (rod opsin or rhodopsin-like-1) expressed in rods and two cone opsins, namely LWS (long-wavelength-sensitive) and SWS1 (short-wavelength-sensitive-1) genes. Until recently, the study of snake photopigments has been largely ignored. However, its importance has become clear within the past few years as studies reconsider Walls’ transmutation theory, which was first proposed in the 1930s. In this study, the visual pigments of Bothrops atrox (the common lancehead), a South American pit viper, were examined. Specifically, full-length RH1 and LWS opsin gene sequences were cloned, as well as most of the SWS1 opsin gene. These sequences were subsequently used for phylogenetic analysis and to predict the wavelength of maximum absorbance (λmax) for each photopigment. This is the first report to support the potential for rudimentary color vision in a South American viper, specifically a species that is regarded as being nocturnal.

scholarly journals Types of E-Procurement Systems and Technologies Used in the Nigerian Construction Environment

2020 ◽  
Vol 9 (4) ◽  
pp. 1444-1452
Keyword(s):  
Construction Project ◽  
Project Delivery ◽  
Limited Capacity ◽  
Web Portals ◽  
Construction Sites ◽  
The Past ◽  
Different Types ◽  
The Common ◽  
E Mail ◽  
Construction Works

The use of e-Procurement in the acquisition of construction works and services has witnessed a tremendous growth in the past three decades across the world. However, in a developing country like Nigeria, there is the lack of understanding of the different types of e-Procurement systems and specific technologies used to support the execution of construction procurement tasks. This study, therefore, relied on a questionnaire survey of 759 users of e-Procurement to systematically identify the different types of e-Procurement systems and technologies used in the Nigerian construction environment. The results of data analysis revealed that whereas the common e-Procurement systems used in the study area are those that help in disseminating/receiving information on tender opportunities, exchanging construction project information/data, submitting tenders, awarding contracts, placing orders and making/receiving payment for materials/equipment and services, the use of systems that help in tracking the movement of materials/equipment and monitoring the progress of work on construction sites was not very common. In addition, it was also found that the main e-Procurement technologies used to support the execution of construction procurement activities in the study area were e-Mails, websites and web portals. The study concludes that the over reliance on simple e-Procurement technologies such as e-Mail and websites/portals with limited capacity to engender collaboration, integration and coordination of tasks is inconsistent with the growing sophistication and advancement in construction procurement activities and processes and that this has a tendency to limit the benefits associated with e-Procurement in construction project delivery in Nigeria.

Study of the Molecular Architecture of Keratin Filaments by Electron Microscopy

1982 ◽  
Vol 40 ◽  
pp. 118-119
Author(s):  
U. Aebi ◽  
P. Rew ◽  
T.-T. Sun
Keyword(s):  
Electron Microscopy ◽  
Structural Organization ◽  
Cell Types ◽  
Structural Features ◽  
Molecular Architecture ◽  
The Past ◽  
Keratin Filaments ◽  
Different Types ◽  
10 Nm Filaments ◽  
Different Cell Types

Various types of intermediate-sized (10-nm) filaments have been found and described in many different cell types during the past few years. Despite the differences in the chemical composition among the different types of filaments, they all yield common structural features: they are usually up to several microns long and have a diameter of 7 to 10 nm; there is evidence that they are made of several 2 to 3.5 nm wide protofilaments which are helically wound around each other; the secondary structure of the polypeptides constituting the filaments is rich in ∞-helix. However a detailed description of their structural organization is lacking to date.

On the assembly and structural modulation of lens fiber junctions

1984 ◽  
Vol 42 ◽  
pp. 110-113
Author(s):  
E.L. Benedetti ◽  
I. Dunia ◽  
Do Ngoc Lien ◽  
O. Vallon ◽  
D. Louvard ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Natural History ◽  
Intercellular Junctions ◽  
Eye Lens ◽  
Membrane Domains ◽  
Functional Polymorphism ◽  
Lens Fiber ◽  
The Past ◽  
Structural Modulation ◽  
Biochemical Difference

In the eye lens emerging molecular and structural patterns apparently cohabit with the remnants of the past. The lens in a rather puzzling fashion sums up its own natural history and even transient steps of the differentiation are memorized. A prototype of this situation is well outlined by the study of the lenticular intercellular junctions. These membrane domains exhibit structural, biochemical and perhaps functional polymorphism reflecting throughout life the multiple steps of the differentiation of the epithelium into fibers and of the ageing process of the lenticular cells.The most striking biochemical difference between the membrane derived from the epithelium and from the fibers respectively, concerns the presence of the 26,000 molecular weight polypeptide (MP26) in the latter membranes.

Beyond Promoter: The Role of Macrophage in Invasion and Progression of Renal Cell Carcinoma

2020 ◽  
Vol 15 (7) ◽  
pp. 588-596
Author(s):  
Haibao Zhang ◽  
Guodong Zhu
Keyword(s):  
Renal Cell Carcinoma ◽  
Tumor Microenvironment ◽  
Cell Carcinoma ◽  
Renal Cell ◽  
Cell Formation ◽  
Biological Behavior ◽  
Tumor Stem Cell ◽  
The Past ◽  
The Common

Renal cell carcinoma (RCC) is one of the common urologic neoplasms, and its incidence has been increasing over the past several decades; however, its pathogenesis is still unknown up to now. Recent studies have found that in addition to tumor cells, other cells in the tumor microenvironment also affect the biological behavior of the tumor. Among them, macrophages exist in a large amount in tumor microenvironment, and they are generally considered to play a key role in promoting tumorigenesis. Therefore, we summarized the recent researches on macrophage in the invasiveness and progression of RCC in latest years, and we also introduced and discussed many studies about macrophage in RCC to promote angiogenesis by changing tumor microenvironment and inhibit immune response in order to activate tumor progression. Moreover, macrophage interactes with various cytokines to promote tumor proliferation, invasion and metastasis, and it also promotes tumor stem cell formation and induces drug resistance in the progression of RCC. The highlight of this review is to make a summary of the roles of macrophage in the invasion and progression of RCC; at the same time to raise some potential and possible targets for future RCC therapy.

Is Healthcare Special?

2018 ◽  
Author(s):  
Gordon Moore ◽  
John A. Quelch ◽  
Emily Boudreau
Keyword(s):  
Consumer Choice ◽  
Special Relationship ◽  
Individual Choice ◽  
Health Consequences ◽  
Critical Question ◽  
The Past ◽  
Different Types ◽  
Collective Benefit ◽  
Patient Ethics

Chapter 2 asks the critical question of whether healthcare is different from other consumer-driven markets. In the past, many pushed back on the notion that healthcare could be a consumer-driven industry, arguing that it is fundamentally different from other markets. This chapter acknowledges and reviews these critiques, highlighting four areas that might present challenges to increasing consumer choice in healthcare: the special relationship between doctor and patient, ethics and morality, individual choice versus collective benefit, and the health consequences of consumer choice. In doing so, this chapter also presents a schematic for thinking about the different types of healthcare choices, arguing that not all choices are equal and consumers may be more prepared to make decisions in some areas as opposed to others. In presenting the counterargument to consumer choice, this chapter asks the reader to consider the drawbacks and potential limitations of consumer choice in healthcare.

Searching for Political Parties in the Past

2017 ◽  
Author(s):  
Piero Ignazi
Keyword(s):  
Eighteenth Century ◽  
Political Parties ◽  
Political Party ◽  
Ancient Greece ◽  
Political Community ◽  
Democratic Politics ◽  
The Political ◽  
The Past ◽  
The Common

Chapter 1 introduces the long and difficult process of the theoretical legitimation of the political party as such. The analysis of the meaning and acceptance of ‘parties’ as tools of expressing contrasting visions moves forward from ancient Greece and Rome where (democratic) politics had first become a matter of speculation and practice, and ends up with the first cautious acceptance of parties by eighteenth-century British thinkers. The chapter explores how parties or factions have been constantly considered tools of division of the ‘common wealth’ and the ‘good society’. The holist and monist vision of a harmonious and compounded society, stigmatized parties and factions as an ultimate danger for the political community. Only when a new way of thinking, that is liberalism, emerged, was room for the acceptance of parties set.

Vietnamese Historical Writing

2018 ◽  
Author(s):  
Patricia Pelley
Keyword(s):  
Cold War ◽  
East Asian ◽  
History Writing ◽  
Southern State ◽  
The Past ◽  
South Vietnam ◽  
Political Function ◽  
Different Types ◽  
The Cold War ◽  
North Vietnam

This chapter demonstrates how the process of decolonization and the ensuing separation of Vietnam into a northern and southern state as part of the Cold War in Asia led to different types of history-writing. In both Vietnamese regimes, the writing of history had to serve the state, and in both countries historians emphasized its political function. Whereas North Vietnam located itself in an East Asian and Marxist context, historians of South Vietnam positioned it within a Southeast Asian setting and took a determinedly anti-communist position. After 1986—over a decade after reunification—with past tensions now relaxed, the past could be revaluated more openly under a reformist Vietnamese government that now also permitted much greater interaction with foreign historians.

Can Groups Assert That P?

2019 ◽  
pp. 326-344
Author(s):  
Deborah Tollefsen
Keyword(s):  
Common Ground ◽  
Speech Act ◽  
Single Individual ◽  
Constitutive Rule ◽  
The Past ◽  
Group Members ◽  
The Common ◽  
Declarative Statement ◽  
John Macfarlane

When a group or institution issues a declarative statement, what sort of speech act is this? Is it the assertion of a single individual (perhaps the group’s spokesperson or leader) or the assertion of all or most of the group members? Or is there a sense in which the group itself asserts that p? If assertion is a speech act, then who is the actor in the case of group assertion? These are the questions this chapter aims to address. Whether groups themselves can make assertions or whether a group of individuals can jointly assert that p depends, in part, on what sort of speech act assertion is. The literature on assertion has burgeoned over the past few years, and there is a great deal of debate regarding the nature of assertion. John MacFarlane has helpfully identified four theories of assertion. Following Sandy Goldberg, we can call these the attitudinal account, the constitutive rule account, the common-ground account, and the commitment account. I shall consider what group assertion might look like under each of these accounts and doing so will help us to examine some of the accounts of group assertion (often presented as theories of group testimony) on offer. I shall argue that, of the four accounts, the commitment account can best be extended to make sense of group assertion in all its various forms.

Sign in / Sign up

Export Citation Format

Share Document