scholarly journals Quaternary Misfit Compounds—A Concise Review

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 468
Author(s):  
Sokhrab B. Aliev ◽  
Reshef Tenne
Keyword(s):  
Irrational Number ◽  
Short Review ◽  
Layered Compounds ◽  
Layered Compound ◽  
Charge Carrier Density ◽  
Precise Control ◽  
Rocksalt Structure ◽  
Main Emphasis ◽  
Recent Developments ◽  
Metal Dichalcogenides

Misfit layered compounds (MLCs) have been studied in the literature for the last 40 years. They are generally made of an alternating sequence of two monolayers, a distorted rocksalt structure, and a hexagonal layered compound. In a typical MLC, the c-axis is common to the two monolayers and so is one of the axes in the layer plan. However, the two compounds are non-commensurate along at least one axis, and the ratio between the two axes is an irrational number making the MLC a non-stoichiometric compound. The two main families of MLC are those based on metal dichalcogenides and CoO2 as the hexagonal layered compound. Traditionally, ternary MLCs were prepared and studied, but some quaternary and multinary MLC minerals have been known for many years. Over the last few years, interest in MLCs with four and even larger number of atoms has grown. Doping or alloying of a ternary MLC permits precise control of the charge carrier density and hence the electrical, thermoelectric, catalytic, and optical properties of such compounds. In this short review, some of these developments will be discussed with the main emphasis put on quaternary MLC nanotubes belonging to the chalcogenide series. The synthesis, structural characterization, and some of their properties are considered. Some recent developments in quaternary cobaltite MLCs and recent studies on exfoliated MLCs are discussed as well.

Recent Developments in C–C Bond Formation Using Catalytic Reductive Coupling Strategies

Synthesis ◽  
2020 ◽  
Vol 52 (18) ◽  
pp. 2623-2638
Author(s):  
Joshua D. Sieber ◽  
Toolika Agrawal
Keyword(s):  
Bond Formation ◽  
Cross Coupling ◽  
Short Review ◽  
Reductive Coupling ◽  
Recent Developments ◽  
Molecular Complexity ◽  
Metal Catalyzed ◽  
Coupling Processes ◽  
Coupling Strategies

Metal-catalyzed reductive coupling processes have emerged as a powerful methodology for the introduction of molecular complexity from simple starting materials. These methods allow for an orthogonal approach to that of redox-neutral strategies for the formation of C–C bonds by enabling cross-coupling of starting materials not applicable to redox-neutral chemistry. This short review summarizes the most recent developments in the area of metal-catalyzed reductive coupling utilizing catalyst turnover by a stoichiometric reductant that becomes incorporated in the final product.1 Introduction2 Ni Catalysis3 Cu Catalysis4 Ru, Rh, and Ir Catalysis4.1 Alkenes4.2 1,3-Dienes4.3 Allenes4.4 Alkynes4.5 Enynes5 Fe, Co, and Mn Catalysis6 Conclusion and Outlook

Recent Developments in Mechanical Specimen Preparation for Tem and Sem Applications

1999 ◽  
Vol 5 (S2) ◽  
pp. 932-933
Author(s):  
W. Li ◽  
S. Q. Wang ◽  
R. Trussell ◽  
M. Xu ◽  
R.D. Venables ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Integrated Circuits ◽  
Sample Preparation ◽  
Ion Beam ◽  
Wedge Angle ◽  
Specimen Preparation ◽  
Precise Control ◽  
Transmission Electron ◽  
Recent Developments ◽  
Polishing Tool

The continued reduction in the size of critical features in integrated circuits has resulted in the need to develop rapid, site-specific, sectioning techniques to enable efficient physical characterization of the structures of interest. We have implemented a mechanical polishing approach to achieve this objective with the additional goals of maximizing the number of targeted sites in a sample that can be analyzed, and minimizing physically destructive procedures, such as ion beam exposure. Precision sample preparation approaches have been under investigation for both transmission electron microscopy and scanning electron microscopy.The mechanical specimen preparation approach used in this work is a variant of the well-known wedge polishing technique. Here we use a polishing tool that does not contact the grinding surface, thus allowing precise control of the wedge angle. Prior to sample preparation, the polishing tool head was precision aligned parallel to the platen.

scholarly journals THE INTERFACE OF COSMOLOGY WITH STRING AND M(ILLENNIUM) THEORY

2001 ◽  
Vol 16 (30) ◽  
pp. 4803-4843 ◽  
Author(s):  
DAMIEN A. EASSON
Keyword(s):  
Early Universe ◽  
Extra Dimensions ◽  
Large Extra Dimensions ◽  
Short Review ◽  
Big Bang ◽  
Space Time ◽  
String Cosmology ◽  
Brane World ◽  
Recent Developments ◽  
M Theory

The purpose of this review is to discuss recent developments occurring at the interface of cosmology with string and M theory. We begin with a short review of 1980s string cosmology and the Brandenberger–Vafa mechanism for explaining space–time dimensionality. It is shown how this scenario has been modified to include the effects of p-brane gases in the early universe. We then introduce the Pre-Big-Bang scenario (PBB), Hořava–Witten heterotic M theory and the work of Lukas, Ovrut and Waldram, and end with a discussion of large extra dimensions, the Randall–Sundrum model and Brane World cosmologies.

scholarly journals A Short Review on Recent Developments in TMD Factorization and Implementation

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
Ignazio Scimemi
Keyword(s):  
Transverse Momentum ◽  
Perturbative Qcd ◽  
Short Review ◽  
Transverse Momentum Dependent ◽  
Recent Developments

In the latest years the theoretical and phenomenological advances in the factorization of several collider processes using the transverse momentum dependent distributions (TMD) have greatly increased. I attempt here a short resume of the newest developments discussing also the most recent perturbative QCD calculations. The work is not strictly directed to experts in the field and it wants to offer an overview of the tools and concepts which are behind the TMD factorization and evolution. I consider both theoretical and phenomenological aspects, some of which have still to be fully explored. It is expected that actual colliders and the Electron Ion Collider (EIC) will provide important information in this respect.

scholarly journals State of the Art in Alcohol Sensing with 2D Materials

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Ramin Boroujerdi ◽  
Amor Abdelkader ◽  
Richard Paul
Keyword(s):  
State Of The Art ◽  
2D Materials ◽  
Chemical Species ◽  
Weight Ratio ◽  
Layered Compounds ◽  
Single Atom ◽  
Future Research ◽  
Essential Factor ◽  
New Materials ◽  
Recent Developments

AbstractSince the discovery of graphene, the star among new materials, there has been a surge of attention focused on the monatomic and monomolecular sheets which can be obtained by exfoliation of layered compounds. Such materials are known as two-dimensional (2D) materials and offer enormous versatility and potential. The ultimate single atom, or molecule, thickness of the 2D materials sheets provides the highest surface to weight ratio of all the nanomaterials, which opens the door to the design of more sensitive and reliable chemical sensors. The variety of properties and the possibility of tuning the chemical and surface properties of the 2D materials increase their potential as selective sensors, targeting chemical species that were previously difficult to detect. The planar structure and the mechanical flexibility of the sheets allow new sensor designs and put 2D materials at the forefront of all the candidates for wearable applications. When developing sensors for alcohol, the response time is an essential factor for many industrial and forensic applications, particularly when it comes to hand-held devices. Here, we review recent developments in the applications of 2D materials in sensing alcohols along with a study on parameters that affect the sensing capabilities. The review also discusses the strategies used to develop the sensor along with their mechanisms of sensing and provides a critique of the current limitations of 2D materials-based alcohol sensors and an outlook for the future research required to overcome the challenges.

scholarly journals Study of the textural properties of some layered double hydroxides

2013 ◽  
Vol 21 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Cornelia-Magda Puscasu ◽  
Carmen Gherasim ◽  
Dragos Mardare ◽  
Gabriela Carja
Keyword(s):  
Layered Double Hydroxides ◽  
Structural Characteristics ◽  
Chemical Species ◽  
Textural Properties ◽  
Layered Compounds ◽  
Layered Compound ◽  
X Ray Diffraction ◽  
Anionic Clays ◽  
Interlayer Region ◽  
Double Hydroxides

Abstract Layered double hydroxides (LDHs) are one of the nano ordered layered compounds. The importance of layered compound is based on their ability to retain chemical species with electrical charges compatible to those of the layers. They may be used in areas such as catalysis, industry, medicine, environmental protection, construction etc. Layered double hydroxides are anionic clays comprising positively charged layers with anions and water molecules intercalated in the interlayer region. The aim of this work was to obtain Cu and/or Ni substituted layered double hydroxides with different micromorphology characteristics. The obtained results pointed out that the relationship between LDHs composition and their textural properties can be controlled. The layered double hydroxides samples were fabricated by using direct coprecipitation method. Field Emission Scanning Electron Microscope (FE-SEM) and X-Ray Diffraction (XRD) analyses were used to study the textural characteristics and the structural characteristics of the samples.

scholarly journals HLA Expression at the Maternal-Fetal Interface

1998 ◽  
Vol 6 (3-4) ◽  
pp. 197-204 ◽  
Author(s):  
Heinz Hutter ◽  
Astrid Hammer ◽  
Gottfried Dohr ◽  
Joan S. Hunt
Keyword(s):  
Immune System ◽  
Hla Class I ◽  
Short Review ◽  
Maternal Blood ◽  
Protective Mechanisms ◽  
Hla Class I Molecules ◽  
Recent Developments ◽  
The Subject ◽  
Class Ii Antigens ◽  
Maternal Fetal Interface

Pregancy in the human presents an “immunological paradox,” because of the unexpected willingness of mothers to accept genetically disparate tissues. The fact that the fetus can develop unharmed for nine months shows that protective mechanisms must exist to permit its survival. The conditions that permit the genetically dissimilar human fetus to evade rejection by its mother's immune system have been the subject of intense interest for several decades. As the placental cells, which are in contact with maternal blood or tissue, are devoid of HLA class II antigens, interest has focused on the expression of HLA class molecules. Recent developments in the constitutive, transcriptional, and translational expression of HLA class I molecules on anatomically and morphologically different subpopulations of trophoblast cells will form the basis of this short review.

Solid State Synthesis and Characterization of Tin-Based Low-Dimensional Materials

2002 ◽  
Vol 755 ◽  
Author(s):  
Tolulope O. Salami ◽  
Scott R. J. Oliver
Keyword(s):  
Variable Temperature ◽  
Layered Compounds ◽  
Layered Compound ◽  
X Ray Diffraction ◽  
Group 14 ◽  
Potential Applications ◽  
Low Dimensional ◽  
2D And 3D ◽  
Extended Materials

ABSTRACTWe report the synthetic conditions, physical properties and potential applications of late group 14 metal (Sn) 0D, 1D, 2D and 3D extended materials. The structures are primarily neutral chain and anionic layered compounds. The latter are charge-balanced by ammonium cations, as in and BING-7 [Sn(C2O4)F-] [NH4+] and BING-8 [Sn(PO4H)F-] [NH4+]. The neutral layered compound and chain compounds BING-1 [Na4Sn4(C2O4)F6], BING-2 [KSn(C2O4)F] and BING-4 [Sn(C2O4)(C5H5N)] have also been synthesized solvothermally. Thermogravimetric analysis (TGA) under nitrogen and in-situ variable temperature X-ray diffraction show that the materials decompose in the 200°C to 300°C range to more stable phases. Nuclear magnetic resonance (NMR) was used to monitor the ion-exchange properties of some of the materials. The intercalation properties of these materials are still being investigated.

Surface Modification of Synthesized Layered Double Hydroxide [LDH] for Methylene Blue Dye Removal in Textile Industry via Photocatalytic Activity under Visible Light

2017 ◽  
Vol 46 ◽  
pp. 135-147 ◽  
Author(s):  
K. Gohatre Omdeo ◽  
Vasudeo Rane Ajay ◽  
Kanny Krishnan ◽  
V.K. Abitha ◽  
Nikesh Samarth ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Photocatalytic Activity ◽  
Visible Light ◽  
Layered Double Hydroxide ◽  
Layered Compounds ◽  
Layered Compound ◽  
Ammonium Bromide ◽  
X Ray ◽  
Surface Modified ◽  
Double Hydroxide

Layered double hydroxides (abbreviated as LDHs) are one of the nanoordered layered compounds. The importance of layered compound is based on their ability to retain chemical species with electrical charges compatible to those of the layers. In this study we have reported the synthesis of nanosized layered double hydroxide (LDH) by co-precipitation method using two different surfactants as cetyl trimethyl ammonium bromide (CTAB) and octadecyl trimethyl ammonium bromide (ODTMA) having different critical micelle concentration (CMC) /chain length and its comparative results on calcined surface modified LDH (CS-LDH). The structure of surface modified layered double hydroxide (CS-LDH) synthesized is unique and has important advantages to the photocatalytic activity. LDH has significant number of application due to their structural, chemical properties etc., these compounds can be used as catalyst, adsorbents, anion exchanger. The photocatalytic activity of prepared surface modified CS-LDH was tested on degradation of the methylene blue (MB) dye in an aqueous solution. The surface characteristics of LDH and CS-LDH were examined using Energy Dispersive X-ray (EDX), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and UV-Visible spectrophotometer for Photocatalytic activity under visible light using MB dye. It was observed that highly exfoliated and basal spacing in CS-LDH-ODTMA which enhanced photocatalytic activity (Approx. 60% degradation) than that of comparison to CS-LDH-CTAB (Approx. 32% degradation).

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