Mechanism of zeolites crystal growth: new findings and open questions

CrystEngComm ◽  
2016 ◽  
Vol 18 (5) ◽  
pp. 650-664 ◽  
Author(s):  
Julien Grand ◽  
Hussein Awala ◽  
Svetlana Mintova
Keyword(s):  
Crystal Growth ◽  
Open Questions ◽  
New Findings

scholarly journals Intraspecific variation in the Cambrian: new observations on the morphology of the Chengjiang euarthropod Sinoburius lunaris

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Michel Schmidt ◽  
Yu Liu ◽  
Xianguang Hou ◽  
Joachim T. Haug ◽  
Carolin Haug ◽  
...  
Keyword(s):  
Intraspecific Variation ◽  
Southwest China ◽  
3D Models ◽  
Morphological Characters ◽  
Open Questions ◽  
New Findings ◽  
Unique Shape ◽  
Variable Species ◽  
Chengjiang Biota ◽  
3D Software

Abstract Background The Chengjiang biota from southwest China (518-million-years old, early Cambrian) has yielded nearly 300 species, of which more than 80 species represent early chelicerates, crustaceans and relatives. The application of µCT-techniques combined with 3D software (e.g., Drishti), has been shown to be a powerful tool in revealing and analyzing 3D features of the Chengjiang euarthropods. In order to address several open questions that remained from previous studies on the morphology of the xandarellid euarthropod Sinoburius lunaris, we reinvestigated the µCT data with Amira to obtain a different approach of visualization and to generate new volume-rendered models. Furthermore, we used Blender to design 3D models showing aspects of intraspecific variation. Results New findings are: (1) antennulae consist of additional proximal articles that have not been detected before; (2) compared to other appendages, the second post-antennular appendage has a unique shape, and its endopod is comprised of only five articles (instead of seven); (3) the pygidium bears four pairs of appendages which are observed in all specimens. On the other hand, differences between specimens also have been detected. These include the presence/absence of diplotergites resulting in different numbers of post-antennular appendages and tergites and different distances between the tip of the hypostome and the anterior margin of the head shield. Conclusions Those new observations reveal intraspecific variation among Chengjiang euarthropods not observed before and encourage considerations about possible sexual dimorphic pairs or ontogenetic stages. Sinoburius lunaris is a variable species with respect to its morphological characters, cautioning that taxon-specific variabilities need to be considered when exploring new species.

Open Issues in SiC Bulk Growth

2014 ◽  
Vol 778-780 ◽  
pp. 3-8 ◽  
Author(s):  
Didier Chaussende ◽  
Kanaparin Ariyawong ◽  
Nikolaos Tsavdaris ◽  
Martin Seiss ◽  
Yun Ji Shin ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Industrial Development ◽  
Growth Process ◽  
Special Focus ◽  
Development Problem ◽  
Bulk Growth ◽  
Crystal Growth Process ◽  
Open Questions ◽  
Process Chemistry ◽  
Open Issues

In this paper, an overview of the SiC bulk growth processes is given with a special focus on the most recent results related to growth and modeling. In addition, even if SiC growth is a very old topic and that it is now considered as an « industrial development problem », we will show that there are still many open questions of both fundamental and technological importance related to its crystal growth. Process chemistry and surface mechanisms will be more specifically discussed.

scholarly journals Dispatching plasma membrane cholesterol and Sonic Hedgehog dispatch: two sides of the same coin?

2021 ◽  
Author(s):  
Kristina Ehring ◽  
Kay Grobe
Keyword(s):  
Plasma Membrane ◽  
Cell Fate ◽  
Signal Sequence ◽  
Target Cells ◽  
Cell Fate Decisions ◽  
Open Questions ◽  
New Findings ◽  
Resistance Nodulation Division ◽  
Rnd Transporter ◽  
Niemann Pick

Vertebrate and invertebrate Hedgehog (Hh) morphogens signal over short and long distances to direct cell fate decisions during development and to maintain tissue homeostasis after birth. One of the most important questions in Hh biology is how such Hh signaling to distant target cells is achieved, because all Hh proteins are secreted as dually lipidated proteins that firmly tether to the outer plasma membrane leaflet of their producing cells. There, Hhs multimerize into light microscopically visible storage platforms that recruit factors required for their regulated release. One such recruited release factor is the soluble glycoprotein Scube2 (Signal sequence, cubulin domain, epidermal-growth-factor-like protein 2), and maximal Scube2 function requires concomitant activity of the resistance-nodulation-division (RND) transporter Dispatched (Disp) at the plasma membrane of Hh-producing cells. Although recently published cryo-electron microscopy-derived structures suggest possible direct modes of Scube2/Disp-regulated Hh release, the mechanism of Disp-mediated Hh deployment is still not fully understood. In this review, we discuss suggested direct modes of Disp-dependent Hh deployment and relate them to the structural similarities between Disp and the related RND transporters Patched (Ptc) and Niemann-Pick type C protein 1. We then discuss open questions and perspectives that derive from these structural similarities, with particular focus on new findings that suggest shared small molecule transporter functions of Disp to deplete the plasma membrane of cholesterol and to modulate Hh release in an indirect manner.

Greek Lists of the Apostles: New Findings and Open Questions

2016 ◽  
Vol 20 (3) ◽  
Author(s):  
Christophe Guignard
Keyword(s):  
Preliminary Report ◽  
Basic Information ◽  
Research Project ◽  
Open Questions ◽  
New Findings ◽  
Textual Traditions ◽  
New Research

Abstract:From the 4th/5th century on, one finds in virtually all the languages of early and mediaeval Christianity lists providing basic information about the apostles, which form a large and prolific tradition. Dealing with the Twelve (and Paul), and/or the seventy disciples of Luke 10, these lists bring together biblical and traditional or apocryphal data: for the Twelve and Paul, mainly the regions that they evangelised, their martyrdom and their burial place; for the Seventy, mainly their episcopal sees. Most of the major texts were edited by Theodor Schermann in 1907, but the apostle lists were afterwards largely neglected by scholars. Conceived as a preliminary report on a new research project on theses texts, this article deals with the identification of many new Greek witnesses, before focusing on two particular textual traditions on which the results attained so far shed new light: firstly, the

Montmorillonite Dendrites

1974 ◽  
Vol 32 ◽  
pp. 454-455
Author(s):  
Necip Güven ◽  
Rodney W. Pease
Keyword(s):  
Crystal Growth ◽  
Growth Mechanism ◽  
Growth Front ◽  
Morphological Features ◽  
Dendritic Crystal ◽  
Crystal Growth Mechanism

Morphological features of montmorillonite aggregates in a large number of samples suggest that they may be formed by a dendritic crystal growth mechanism (i.e., tree-like growth by branching of a growth front).

TEM and cathodoluminescence of precipitates in II-VI semiconductors

1988 ◽  
Vol 46 ◽  
pp. 488-489
Author(s):  
Joanna L. Batstone
Keyword(s):  
Crystal Growth ◽  
Band Gap ◽  
Local Strain ◽  
Wide Band ◽  
Optoelectronic Device ◽  
Wide Band Gap ◽  
Bulk Crystal Growth ◽  
Transmission Electron ◽  
Device Applications ◽  
Stoichiometry Control

Interest in II-VI semiconductors centres around optoelectronic device applications. The wide band gap II-VI semiconductors such as ZnS, ZnSe and ZnTe have been used in lasers and electroluminescent displays yielding room temperature blue luminescence. The narrow gap II-VI semiconductors such as CdTe and HgxCd1-x Te are currently used for infrared detectors, where the band gap can be varied continuously by changing the alloy composition x.Two major sources of precipitation can be identified in II-VI materials; (i) dopant introduction leading to local variations in concentration and subsequent precipitation and (ii) Te precipitation in ZnTe, CdTe and HgCdTe due to native point defects which arise from problems associated with stoichiometry control during crystal growth. Precipitation is observed in both bulk crystal growth and epitaxial growth and is frequently associated with segregation and precipitation at dislocations and grain boundaries. Precipitation has been observed using transmission electron microscopy (TEM) which is sensitive to local strain fields around inclusions.

STM studies of crystal growth

1991 ◽  
Vol 49 ◽  
pp. 374-375
Author(s):  
M. G. Lagally
Keyword(s):  
Crystal Growth ◽  
Molecular Beam ◽  
Chemical Vapor ◽  
Sputter Deposition ◽  
Field Of View ◽  
Scanning Tunneling ◽  
Wide Field ◽  
Tunneling Microscopy ◽  
Wide Field Of View ◽  
The One

It has been recognized since the earliest days of crystal growth that kinetic processes of all Kinds control the nature of the growth. As the technology of crystal growth has become ever more refined, with the advent of such atomistic processes as molecular beam epitaxy, chemical vapor deposition, sputter deposition, and plasma enhanced techniques for the creation of “crystals” as little as one or a few atomic layers thick, multilayer structures, and novel materials combinations, the need to understand the mechanisms controlling the growth process is becoming more critical. Unfortunately, available techniques have not lent themselves well to obtaining a truly microscopic picture of such processes. Because of its atomic resolution on the one hand, and the achievable wide field of view on the other (of the order of micrometers) scanning tunneling microscopy (STM) gives us this opportunity. In this talk, we briefly review the types of growth kinetics measurements that can be made using STM. The use of STM for studies of kinetics is one of the more recent applications of what is itself still a very young field.

Cristal-growth dynamics of n-doped gaAs

1992 ◽  
Vol 50 (2) ◽  
pp. 1544-1545
Author(s):  
Pham V. Huong ◽  
Stéphanie Bouchet ◽  
Jean-Claude Launay
Keyword(s):  
Crystal Growth ◽  
Spatial Resolution ◽  
Epitaxial Layer ◽  
Outer Surface ◽  
Gaas Substrate ◽  
Structural Modification ◽  
Growth Dynamics ◽  
Argon Laser ◽  
High Anisotropy ◽  
Crystal Gaas

Microstructure of epitaxial layers of doped GaAs and its crystal growth dynamics on single crystal GaAs substrate were studied by Raman microspectroscopy with a Dilor OMARS instrument equipped with a 1024 photodiode multichannel detector and a ion-argon laser Spectra-Physics emitting at 514.5 nm.The spatial resolution of this technique, less than 1 μm2, allows the recording of Raman spectra at several spots in function of thickness, from the substrate to the outer deposit, including areas around the interface (Fig.l).The high anisotropy of the LO and TO Raman bands is indicative of the orientation of the epitaxial layer as well as of the structural modification in the deposit and in the substrate at the interface.With Sn doped, the epitaxial layer also presents plasmon in Raman scattering. This fact is already very well known, but we additionally observed that its frequency increases with the thickness of the deposit. For a sample with electron density 1020 cm-3, the plasmon L+ appears at 930 and 790 cm-1 near the outer surface.

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