Supercrystallography-Based Decoding of Structure and Driving Force of Nanocrystal Assembly

Nanocrystal (NC) assembly appears as one promising method towards the controllable design and fabrication of advanced materials with desired property and functionality. The achievement of a “materials-by-design” requires not only a primary structural decoding of NC assembled supercrystal at a wide range of length scales, but also an improved understanding of the interactions and changeable roles of various driving forces over the course of nucleation and growth of NC superlattice. The recent invention of a synchrotron-based X-ray supercrystallographic approach makes it feasible to uncover the structural details of NC-assembled supercrystal at unprecedented levels from atomic through nano to mesoscale. Such structural documentations can be used to trace how various driving forces interact in a competitive way and thus change relatively in strength to govern the formation of individual superlattices under certain circumstances. This short review makes use of four single supercrystals typically made up of spherical, truncate, cubic and octahedral NCs, respectively, and provides a comparable description and a reasonable analysis of the use of a synchrotron-based supercrystallographic approach to reveal various degrees of translational and orientational ordering of NCs within various superlattices. In the connection of observed structural aspects with controlled environments of NC assembly, we further address how various driving forces interact each other to develop relatively changeable roles upon variation of the NC shape to respond to the nucleation and growth of various superlattices. With the guidance of such gained insights, we provide additional examples to illustrate how realistic environments are designed into delicate control of NC assembly to achieve particular interactions between NCs towards harvesting superlattice with NC translational symmetry and atomically crystallographic orientation as desired.

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Directed nucleation and growth by balancing local supersaturation and substrate/nucleus lattice mismatch

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1712911115 ◽

2018 ◽

Vol 115 (14) ◽

pp. 3575-3580 ◽

Cited By ~ 10

Author(s):

L. Li ◽

A. J. Fijneman ◽

J. A. Kaandorp ◽

J. Aizenberg ◽

W. L. Noorduin

Keyword(s):

Self Assembly ◽

Lattice Mismatch ◽

Barium Carbonate ◽

Growth Direction ◽

Nucleation And Growth ◽

Advanced Materials ◽

Carbonate Concentration ◽

Nucleation Barrier ◽

Simultaneous Control ◽

Local Supersaturation

Controlling nucleation and growth is crucial in biological and artificial mineralization and self-assembly processes. The nucleation barrier is determined by the chemistry of the interfaces at which crystallization occurs and local supersaturation. Although chemically tailored substrates and lattice mismatches are routinely used to modify energy landscape at the substrate/nucleus interface and thereby steer heterogeneous nucleation, strategies to combine this with control over local supersaturations have remained virtually unexplored. Here we demonstrate simultaneous control over both parameters to direct the positioning and growth direction of mineralizing compounds on preselected polymorphic substrates. We exploit the polymorphic nature of calcium carbonate (CaCO3) to locally manipulate the carbonate concentration and lattice mismatch between the nucleus and substrate, such that barium carbonate (BaCO3) and strontium carbonate (SrCO3) nucleate only on specific CaCO3 polymorphs. Based on this approach we position different materials and shapes on predetermined CaCO3 polymorphs in sequential steps, and guide the growth direction using locally created supersaturations. These results shed light on nature’s remarkable mineralization capabilities and outline fabrication strategies for advanced materials, such as ceramics, photonic structures, and semiconductors.

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Non-Isothermal Crystallisation Kinetics of Polypropylene at High Cooling Rates and Comparison to the Continuous Two-Domain pvT Model

Polymers ◽

10.3390/polym12071515 ◽

2020 ◽

Vol 12 (7) ◽

pp. 1515

Author(s):

Jonathan Alms ◽

Christian Hopmann ◽

Jian Wang ◽

Tobias Hohlweck

Keyword(s):

Injection Moulding ◽

Polymer Processing ◽

Nucleation And Growth ◽

Growth Theory ◽

Crystallisation Kinetics ◽

Cooling Rates ◽

Dsc Measurements ◽

Wide Range ◽

High Cooling Rates ◽

Kinetics Of

The modelling of the correlation between pressure, specific volume and temperature (pvT) of polymers is highly important for applications in the polymer processing of semi-crystalline thermoplastics, especially in injection moulding. In injection moulding, the polymer experiences a wide range of cooling rates, for example, 60 °C/min near the centre of the part and up to 3000 °C/min near the mould walls. The cooling rate has a high influence on the pvT behaviour, as was shown in the continuous two-domain pvT model (CTD). This work examined the Hoffman–Lauritzen nucleation and growth theory used in the modified Hammami model for extremely high cooling rates (up to 300,000 °C/min) by means of Flash differential scanning calorimeter (DSC) measurements. The results were compared to those of the empirical continuous two-domain pvT model. It is shown that the Hammami model is not suitable to predict the crystallisation kinetics of polypropylene at cooling rates above 600 °C/min, but that the continuous two-domain pvT model is well able to predict crystallisation temperatures at high cooling rates.

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Cell Death and Survival Pathways Involving ATM Protein Kinase

Genes ◽

10.3390/genes12101581 ◽

2021 ◽

Vol 12 (10) ◽

pp. 1581

Author(s):

Toshihiko Aki ◽

Koichi Uemura

Keyword(s):

Cell Death ◽

Protein Kinase ◽

Genotoxic Stress ◽

Short Review ◽

Research Progress ◽

Cellular Protection ◽

Cellular Survival ◽

Cell Death Pathways ◽

Wide Range ◽

Atm Protein

Cell death is the ultimate form of cellular dysfunction, and is induced by a wide range of stresses including genotoxic stresses. During genotoxic stress, two opposite cellular reactions, cellular protection through DNA repair and elimination of damaged cells by the induction of cell death, can occur in both separate and simultaneous manners. ATM (ataxia telangiectasia mutated) kinase (hereafter referred to as ATM) is a protein kinase that plays central roles in the induction of cell death during genotoxic stresses. It has long been considered that ATM mediates DNA damage-induced cell death through inducing apoptosis. However, recent research progress in cell death modality is now revealing ATM-dependent cell death pathways that consist of not only apoptosis but also necroptosis, ferroptosis, and dysfunction of autophagy, a cellular survival mechanism. In this short review, we intend to provide a brief outline of cell death mechanisms in which ATM is involved, with emphasis on pathways other than apoptosis.

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The Ecology of British Upland Landscapes. Ii. The Influence of Policy on The Current Character of The Uplands and The Potential for Change

Journal of Landscape Ecology ◽

10.2478/jlecol-2018-0016 ◽

2018 ◽

Vol 11 (3) ◽

pp. 140-154 ◽

Cited By ~ 3

Author(s):

Robert G.H. Bunce ◽

Claire M. Wood ◽

Simon M. Smart

Keyword(s):

Climate Change ◽

National Parks ◽

Driving Forces ◽

Second World War ◽

High Mountain ◽

Community Ownership ◽

Mountain Habitats ◽

Wide Range ◽

Local Initiatives ◽

Second World

Abstract The paper demonstrates that the British Uplands have been influenced to a great extent by policy - for example, the planting of almost a million hectares of exotic conifers since the Second World War, and the extent of designated areas. Otherwise, climate change transcends policy and is locally important to coastal and high mountain habitats. The different policies affecting the Uplands, such as the Common Agricultural Policy, are described, as are the wide range of designations such as National Parks, which may have a stabilising effect in times of great change. A new trend has started in Scotland in the last 20 years of local initiatives, such as the community ownership of Eigg, however large landowners still dominate. An impact table is presented of the habitats that make up the Uplands and their links to driving forces, with potential changes described that are likely to take place under future policies such as Brexit. Dwarf shrub heath is the habitat affected by many management drivers, whereas habitats such as Inland Rock, are relatively stable but most likely to be affected by climate change.

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Fundamental Design Rules for Turning on Fluorescence in Ionic Molecular Crystals

10.26434/chemrxiv.9890141.v1 ◽

2019 ◽

Author(s):

Christopher R. Benson ◽

Laura Kacenauskaite ◽

Katherine L. VanDenburgh ◽

Wei Zhao ◽

Bo Qiao ◽

...

Keyword(s):

Optical Materials ◽

Advanced Materials ◽

Positive Outcomes ◽

Characteristic Structure ◽

Spectral Shifts ◽

Materials By Design ◽

Homo And Lumo ◽

New Type ◽

Optical Applications ◽

Bright Emission

Fluorescence is critical to many advanced materials including OLEDs and bioimaging. While molecular fluorophores that show bright emission in solution are potential sources of these materials, their emission is frequently lost in the solid state preventing their direct translation to optical applications. Unpredictable packing and coupling of dyes leads to uncontrolled spectral shifts and quenched emission. No universal solution has been found since Perkin made the first synthetic dye 150 years ago. We report the serendipitous discovery of a new type of material that we call small-molecule ionic isolation lattices(SMILES) tackling this long-standing problem. SMILES are easily prepared by adding two equivalents of the anion receptor cyanostar to cationic dyes binding the counter anions and inducing alternating packing of dyes and cyanostar-anion complexes. SMILES materials reinstate solution-like spectral properties and bright fluorescence to thin films and crystals. These positive outcomes derive from the cyanostar. Its wide 3.45-eV band gap allows the HOMO and LUMO levels of the dye to nest inside those of the complex as verified by electrochemistry. This feature simultaneously enables spatial and electronic isolation to decouple the fluorophores from each other and from the cyanostar-anion lattice. Representative dyes from major families of fluorophores, viz, xanthenes, oxazines, styryls, cyanines, and trianguleniums, all crystalize in the characteristic structure and regain their attractive fluorescence. SMILES crystals of rhodamine and cyanine display unsurpassed brightness per volume pointing to uses in demanding applications such as bioimaging. SMILES materials enable predictable fluorophore crystallization to fulfil the promise of optical materials by design.

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In situ X-ray Diffraction Investigation of the Crystallisation of Perfluorinated Ce(IV)-based Metal-Organic Frameworks with UiO-66 and MIL-140 architectures

10.26434/chemrxiv.13252544 ◽

2020 ◽

Author(s):

Stephen Shearan ◽

Jannick Jacobsen ◽

Ferdinando Costantino ◽

Roberto D’Amato ◽

Dmitri Novikov ◽

...

Keyword(s):

Crystal Growth ◽

Metal Organic Frameworks ◽

Building Blocks ◽

Nucleation And Growth ◽

X Ray Diffraction ◽

X Ray ◽

Rate Determining Step ◽

Wide Range ◽

Metal Organic

We report on the results of a thorough in situ synchrotron powder X-ray diffraction study of the crystallisation in aqueous medium of two recently discovered perfluorinated Ce(IV)-based metal-organic frameworks (MOFs), analogues of the already well investigated Zr(IV)-based UiO-66 and MIL-140A, namely, F4_UiO-66(Ce) and F4_MIL-140A(Ce). The two MOFs were originally obtained in pure form in similar conditions, using ammonium cerium nitrate and tetrafluoroterephthalic acid as building blocks, and small variations of the reaction parameters were found to yield mixed phases. Here, we investigate the crystallisation of these compounds in situ in a wide range of conditions, varying parameters such as temperature, amount of the protonation modulator nitric acid (HNO3) and amount of the coordination modulator acetic acid (AcOH). When only HNO3 is present in the reaction environment, F4_MIL-140A(Ce) is obtained as a pure phase. Heating preferentially accelerates nucleation, which becomes rate determining below 57 °C, whereas the modulator influences nucleation and crystal growth to a similar extent. Upon addition of AcOH to the system, alongside HNO3, mixed-phased products, consisting of F4_MIL-140A(Ce) and F4_UiO-66(Ce), are obtained. In these conditions, F4_UiO-66(Ce) is always formed faster and no interconversion between the two phases occurs. In the case of F4_UiO-66(Ce), crystal growth is always the rate determining step. An increase in the amount of HNO3 slows down both nucleation and growth rates for F4_MIL-140A(Ce), whereas nucleation is mainly affected for F4_UiO-66(Ce). In addition, a higher amount HNO3 favours the formation of F4_MIL-140A(Ce). Similarly, increasing the amount of AcOH leads to slowing down of the nucleation and growth rate, but favours the formation of F4_UiO-66(Ce). The pure F4_UiO-66(Ce) phase could also be obtained when using larger amounts of AcOH in the presence of minimal HNO3. Based on these in situ results, a new optimised route to achieving a pure, high quality F4_MIL-140A(Ce) phase in mild conditions (60 °C, 1 h) is also identified.

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Nucleation and Growth of Supported Metal Clusters at Defect Sites on Mgo and NaCl (001) Surfaces: The Cases of Pd and Ag

MRS Proceedings ◽

10.1557/proc-570-51 ◽

1999 ◽

Vol 570 ◽

Cited By ~ 5

Author(s):

J. A. Venables ◽

G. Haas ◽

H. Brune ◽

J.H. Harding

Keyword(s):

Deposition Temperature ◽

Metal Clusters ◽

Variable Temperature ◽

Nucleation And Growth ◽

Force Microscopy ◽

Atomic Force ◽

Defect Sites ◽

Wide Range ◽

Adsorption Surface

ABSTRACTNucleation and growth of metal clusters at defect sites is discussed in terms of rate equation models, which are applied to the cases of Pd and Ag on MgO(001) and NaCl(001) surfaces. Pd/MgO has been studied experimentally by variable temperature atomic force microscopy (AFM). The island density of Pd on Ar-cleaved surfaces was determined in-situ by AFM for a wide range of deposition temperature and flux, and stays constant over a remarkably wide range of parameters; for a particular flux, this plateau extends from 200 K ≤ T ≤ 600 K, but at higher temperatures the density decreases. The range of energies for defect trapping, adsorption, surface diffusion and pair binding are deduced, and compared with earlier data for Ag on NaCl, and with recent calculations for these metals on both NaCl and MgO

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Five-Membered Hetarene N-Oxides: Recent Advances in Synthesis and Reactivity

Synthesis ◽

10.1055/a-1529-7678 ◽

2021 ◽

Author(s):

Leonid Fershtat ◽

Fedor Teslenko

Keyword(s):

Transition Metal ◽

Medicinal Chemistry ◽

Materials Science ◽

State Of The Art ◽

Short Review ◽

Advanced Materials ◽

Metal Free ◽

Recent Advances ◽

Application Potential ◽

Metal Catalyzed

Five-membered heterocyclic N-oxides attracted special attention due to their strong application potential in medicinal chemistry and advanced materials science. In this regard, novel methods for their synthesis and functionalization are constantly required. In this short review, recent state-of-the-art achievements in the chemistry of isoxazoline N-oxides, 1,2,3-triazole 1-oxides and 1,2,5-oxadiazole 2-oxides are briefly summarized. Main routes to transition-metal-catalyzed and metal-free functionalization protocols along with mechanistic considerations are outlined. Transformation patterns of the hetarene N-oxide rings as precursors to other nitrogen heterocyclic systems are also presented.

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Effects of Curcumin on Vessel Formation Insight into the Pro- and Antiangiogenesis of Curcumin

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2019/1390795 ◽

2019 ◽

Vol 2019 ◽

pp. 1-9 ◽

Cited By ~ 9

Author(s):

Ting-ye Wang ◽

Jia-xu Chen

Keyword(s):

Curcuma Longa ◽

Scientific Evidence ◽

Short Review ◽

Dual Effect ◽

Scientific Databases ◽

Wide Range ◽

Available Information ◽

Insight Into

Curcumin is a compound extracted from the Curcuma longa L, which possesses a wide range of pharmacological effects. However, few studies have collected scientific evidence on its dual effect on angiogenesis. The present review gathered the fragmented information available in the literature to discuss the dual effect and possible mechanisms of curcumin on angiogenesis. Available information concerning the effect of curcumin on angiogenesis is compiled from scientific databases, including PubMed and Web of Science using the key term (curcumin and angiogenesis). The results were reviewed to identify relevant articles. Related literature demonstrated that curcumin has antiangiogenesis effect via regulating multiple factors, including proangiogenesis factor VEGF, MMPs, and FGF, both in vivo and in vitro, and could promote angiogenesis under certain circumstances via these factors. This paper provided a short review on bidirectional action of curcumin, which should be useful for further study and application of this compound that require further studies.

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Ontologies for Education and Learning Design

Encyclopedia of Artificial Intelligence ◽

10.4018/978-1-59904-849-9.ch187 ◽

2011 ◽

pp. 1278-1282

Author(s):

Manuel Lama ◽

Eduardo Sánchez

Keyword(s):

Natural Language ◽

Short Review ◽

Learning Objectives ◽

Learning Design ◽

Dublin Core ◽

Teaching Resources ◽

Metadata Standards ◽

Wide Range ◽

Software Platforms ◽

Learning Software

In the last years, the growing of the Internet have opened the door to new ways of learning and education methodologies. Furthermore, the appearance of different tools and applications has increased the need for interoperable as well as reusable learning contents, teaching resources and educational tools (Wiley, 2000). Driven by this new environment, several metadata specifications describing learning resources, such as IEEE LOM (LTCS, 2002) or Dublin Core (DCMI, 2004), and learning design processes (Rawlings et al., 2002) have appeared. In this context, the term learning design is used to describe the method that enables learners to achieve learning objectives after a set of activities are carried out using the resources of an environment. From the proposed specifications, the IMS (IMS, 2003) has emerged as the de facto standard that facilitates the representation of any learning design that can be based on a wide range of pedagogical techniques. The metadata specifications are useful solutions to describe educational resources in order to favour the interoperability and reuse between learning software platforms. However, the majority of the metadata standards are just focused on determining the vocabulary to represent the different aspects of the learning process, while the meaning of the metadata elements is usually described in natural language. Although this description is easy to understand for the learning participants, it is not appropriate for software programs designed to process the metadata. To solve this issue, ontologies (Gómez-Pérez, Fernández-López, and Corcho, 2004) could be used to describe formally and explicitly the structure and meaning of the metadata elements; that is, an ontology would semantically describe the metadata concepts. Furthermore, both metadata and ontologies emphasize that its description must be shared (or standardized) for a given community. In this paper, we present a short review of the main ontologies developed in last years in the Education field, focusing on the use that authors have given to the ontologies. As we will show, ontologies solve issues related with the inconsistencies of using natural language descriptions and with the consensous for managing the semantics of a given specification.

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