Order Superstructures Research Articles

Synthesis, structural phase transition and weak itinerant magnetism in NixNbSe2

The article presents the synthesis, structural and magnetic properties of NixNbSe2 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25). The intercalation limit of Ni in NbSe2 is found to be 25 mol%, above which NiSe appears as a binary impurity phase. Single crystal X-ray diffraction studies show that all the compounds crystallize in the hexagonal P63/mmc space group. However, there is a distinct phase transition beyond x = 0.20 with Ni intercalation in NixNbSe2. The NixNbSe2 compounds crystallized in the parent 2H phase with x value between 0 ≤ x ≤ 0.2. Subsequently, the phase transforms into the 2H(I) phase with an order superstructure of 2 ao × 2 ao × 1 co for 0.20 ≤ x ≤ 0.25 in NixNbSe2. The superstructure formation is attributed to the occupation of Ni at the alternate octahedral voids present in the van der Waals gap of the NbSe2. The XPS results and theoretical analysis clearly show that the intercalation of Ni results in a more metallic character in NixNbSe2. Magnetic measurements on NixNbSe2 (x = 0.05, 0.1, 0.2, 0.25) shows very small magnetic moment at low temperature for all the compounds. Theoretical calculation on Ni0.25NbSe2 shows that the Ni-3d electrons are delocalized and are very weakly spin-polarized, which may be the reason for the experimentally observed weak magnetism in these compounds.

Supramolecular Shish Kebabs: Higher Order Dimeric Structures from Ring-in-Rings Complexes with Conformational Adaptivity.

Use of abiotic chemical systems for understanding higher order superstructures is challenging. Here we report a ring-in-ring(s) system comprising a hydrogen-bonded macrocycle and cyclobis(paraquat-o-phenylene) tetracation (o-Box) or cyclobis(paraquat-p-phenylene) tetracation (CBPQT4+ , p-Box) that assembles to construct discrete higher order structures with adaptive conformation. As indicated by mass spectrometry, computational modeling, NMR spectroscopy, and single-crystal X-ray diffraction analysis, this ring-in-ring(s) system features the box-directed aggregation of multiple macrocycles, leading to generation of several stable species such as H4G (1 a/o-Box) and H5G (1 a/o-Box). Remarkably, a dimeric shish-kebab-like ring-in-rings superstructure H7G2 (1 a/o-Box) or H8G2 (1 a/p-Box) is formed from the coaxial stacking of two ring-in-rings units. The formation of such unique dimeric superstructures is attributed to the large π-surface of this 2D planar macrocycle and the conformational variation of both host and guest.

Supramolecular Shish Kebabs: Higher Order Dimeric Structures from Ring‐in‐Rings Complexes with Conformational Adaptivity

AbstractUse of abiotic chemical systems for understanding higher order superstructures is challenging. Here we report a ring‐in‐ring(s) system comprising a hydrogen‐bonded macrocycle and cyclobis(paraquat‐o‐phenylene) tetracation (o‐Box) or cyclobis(paraquat‐p‐phenylene) tetracation (CBPQT4+, p‐Box) that assembles to construct discrete higher order structures with adaptive conformation. As indicated by mass spectrometry, computational modeling, NMR spectroscopy, and single‐crystal X‐ray diffraction analysis, this ring‐in‐ring(s) system features the box‐directed aggregation of multiple macrocycles, leading to generation of several stable species such as H4G (1 a/o‐Box) and H5G (1 a/o‐Box). Remarkably, a dimeric shish‐kebab‐like ring‐in‐rings superstructure H7G2 (1 a/o‐Box) or H8G2 (1 a/p‐Box) is formed from the coaxial stacking of two ring‐in‐rings units. The formation of such unique dimeric superstructures is attributed to the large π‐surface of this 2D planar macrocycle and the conformational variation of both host and guest.

Highly vertical 3D bio-inspired hierarchical and multiscale superstructures on microcantilever for gas sensing of organophosphorous agents

Microgravimetric sensors offer promising solution to detect volatile compounds. However, they suffer from a low surface-to-volume ratio limiting the maximum amount of adsorbate that can be fixed on their 2D surface. In this study, we report a bio-inspired method to elaborate highly vertical 3D hierarchical and multiscale superstructures in order to greatly increase the surface area of the microcantilever and to capture more molecules in vapor phase. However, building such superstructures on the microcantilever surface remains challenging in terms of structural design and synthesis while preserving a sufficient response of the sensor at low gas concentration. These particular superstructures are inspired from the antenna of the silkmoth Bombyx mori which is composed of a stem with branches on either side, themselves covered with sensilla. A patterned-microcantilever with high-aspect-ratio silicon micropillars is therefore used as support to generate a dense array of titanium dioxide nanorods decorated by goethite nanobranches. 3D hierarchical superstructures show a high enhancement in the response of the sensor to vapor of dimethyl methylphosphonate, a common simulant of sarin considered as one of the most toxic molecules. This design generates mass and surface stress effects under exposure to low vapor concentrations allowing to reach a limit of detection of 3 ppb. The sensor shows also a fast response to a wide range of concentrations. These results provide promising prospects to improve the detection potential of microcantilever-based sensors by using complex superstructures and dedicated materials to generate stress effect on the microcantilever surface and overcome the conventional microcantilever sensors based only on mass variation.

Artificial Water Channels—Progress Innovations and Prospects

Artificial Water Channels—Progress Innovations and Prospects

One-Dimensional Assemblies of Co3O4 Nanoparticles Formed from Cobalt Hydroxide Carbonate Prepared by Bio-Inspired Precipitation within Confined Space

Nanostructured spinel-type cobalt(II,III) oxide (Co3O4) finds applications in a wide range of technological fields including clean energy conversion systems and electrochemical devices. Low-dimensional morphologies have been identified as particularly promising for the optimization of transport characteristics and the design of anisometric building blocks for the controlled assembly into higher order superstructures. We here introduce a facile bio-inspired room-temperature approach to direct precipitation of one-dimensional basic cobalt carbonate as a precursor to Co3O4 by combining confined submicrometer reaction environments with a carboxylated structure-directing polyelectrolyte. Variation of the polymer concentration and molecular weight then affords control over the mode of infiltration into cylindrical track-etch membrane pores. While a high concentration of the polyelectrolyte additive induces the formation of high aspect ratio smooth fibers with a length resembling the entire pore volume, shorter porous rods with a needle-like substructure are deposited at low polymer concentrations or higher molecular weights. The generality of the infiltration mechanism is demonstrated by gradual substitution of Co2+ ions by Mn2+. Calcination pseudomorphically transforms the resulting intramembrane basic cobalt and manganese carbonate rods and fibers into hierarchical one-dimensional oxides with a porous nanoparticle-based mesostructure.

Magnetic and orbital correlations in multiferroic CaMn7O12 probed by x-ray resonant elastic scattering

The quadruple perovskite CaMn$_7$O$_{12}$ is a topical multiferroic, in which the hierarchy of electronic correlations driving structural distortions, modulated magnetism, and orbital order is not well known and may vary with temperature. x-ray resonant elastic scattering (XRES) provides a momentum-resolved tool to study these phenomena, even in very small single crystals, with valuable information encoded in its polarization- and energy-dependence. We present an application of this technique to CaMn$_7$O$_{12}$. By polarization analysis, it is possible to distinguish superstructure reflections associated with magnetic order and orbital order. Given the high momentum resolution, we resolve a previously unknown splitting of an orbital order superstructure peak, associated with a distinct \textit{locked-in} phase at low temperatures. A second set of orbital order superstructure peaks can then be interpreted as a second-harmonic orbital signal. Surprisingly, the intensities of the first- and second-harmonic orbital signal show disparate temperature and polarization dependence. This orbital re-ordering may be driven by an exchange mechanism, that becomes dominant over the Jahn-Teller instability at low temperature.

Flexible Polymer-Assisted Mesoscale Self-Assembly of Colloidal CsPbBr3 Perovskite Nanocrystals into Higher Order Superstructures with Strong Inter-Nanocrystal Electronic Coupling.

Surface-passivating ligands, although ubiquitous to colloidal nanocrystal (NC) syntheses, play a role in assembling NCs into higher order structures and hierarchical superstructures, which has not been demonstrated yet for colloidal CsPbX3 (X = Cl, Br, and I) NCs. In this work, we report that functional poly(ethylene glycols) (PEG6-Y, Y = -COOH and -NH2) represent unique surface-passivating ligands enabling the synthesis of near-uniform CsPbBr3 NCs with diameters of 3.0 nm. The synthesized NCs are assembled into individual pearl necklaces, bundled pearl necklaces, lamellar, and nanorice superstructures, in situ. It is believed a variety of forces, including van der Waals attractions between hydrophilic PEG tails in a nonpolar solvent and dipole-dipole attraction between NCs, drive mesoscale assembly to form superstructures. Furthermore, postsynthetic ligand treatment strengthens the argument for polymer-assisted mesoscale assembly as pearl necklace assemblies can be successfully converted into either lamellar or nanorice structures. We observe an ∼240 meV bathochromic shift in the lowest energy absorption peak of CsPbBr3 NCs when they are present in the lamellar and nanorice assemblies, representing strong inter-NC electronic coupling. Moreover, pearl necklace structures are spontaneously assembled into micrometer length scale twisted ribbon hierarchical superstructures during storage of colloidal CsPbBr3 NCs. The results show that the self-assembled superstructures of CsPbBr3 NCs are now feasible to prepare via template-free synthesis, as self-assembled structures emerge in the bulk solvent, a process that mimics biological systems except for the use of nonbiological surface ligands (PEG6-Y). Taken together, emergent optoelectronic properties and higher order superstructures of CsPbBr3 NCs should aid their potential use in solid-state devices and simplify scalable manufacturing.

Sustainable Design and Synthesis of Shale Gas Processing and Chemical Manufacturing Processes

In this work, we propose a superstructure of integrated shale gas processing and chemical manufacturing processes with 51,840 alternative possible process designs. The superstructure consists of eight sections, namely acid gas removal, dehydration, NGLs recovery, NGLs separation, hydrocarbons conversion, light olefins separation, C4 separation, and acid gas disposal. For the steam cracking reactions in the hydrocarbons conversion section, we optimize the product distributions of steam cracking of ethane, propane, n-butane, and i-butane. Extensive process simulations are performed for all the involved processes in the superstructure in order to collect high-fidelity process data and develop detailed process models for the technology/process alternatives in the superstructure. Next, we propose a multiobjective mixed-integer nonlinear programming (MINLP) superstructure optimization model with five groups of constraints, namely superstructure network configuration constraints, mass balance constraints, energy balance constraints, techno-economic evaluation constraints, environmental impact assessment constraints. Three objective functions are maximizing the net present value per GJ of raw shale gas, minimizing the global warming potential per GJ of raw shale gas, and minimizing the water footprint per GJ of raw shale gas, respectively. A tailored global optimization algorithm is applied to efficiently solve the resulting nonconvex MINLP problem. The application of the proposed framework is illustrated through a case study based on a Marcellus shale gas feed.

Simultaneous Energy and Water Optimisation in Shale Exploration

This work presents a mathematical model for the simultaneous optimisation of water and energy usage in hydraulic fracturing using a continuous time scheduling formulation. The recycling/reuse of fracturing water is achieved through the purification of flowback wastewater using thermally driven membrane distillation (MD). A detailed design model for this technology is incorporated within the water network superstructure in order to allow for the simultaneous optimisation of water, operation, capital cost, and energy used. The study also examines the feasibility of utilising the co-produced gas that is traditionally flared as a potential source of energy for MD. The application of the model results in a 22.42% reduction in freshwater consumption and 23.24% savings in the total cost of freshwater. The membrane thermal energy consumption is in the order of 244 × 103 kJ/m3 of water, which is found to be less than the range of thermal consumption values reported for membrane distillation in the literature. Although the obtained results are not generally applicable to all shale gas plays, the proposed framework and supporting models aid in understanding the potential impact of using scheduling and optimisation techniques to address flowback wastewater management.

Simultaneous optimisation and heat integration of evaporation systems including mechanical vapour recompression and background process

This paper proposes a general superstructure and a Mixed-Integer Nonlinear Programming (MINLP) model for the synthesis and simultaneous optimisation and Heat Integration (HI) of Single- and Multiple-Effect Evaporation (SEE/MEE) systems including Mechanical Vapour Recompression (MVR) and the background process. The proposed superstructure also includes different flow patterns (forward feed, backward feed, parallel feed and mixed feed), Flashing of Condensates (FCs), single- and multi-stage MVR systems and various HI opportunities for preheating of feed stream (e.g. with condensates, bled vapours, and hot streams from the background process). The newly proposed SEE/MEE-FC-MVR superstructure is combined with a Heat Exchanger Network (HEN) superstructure for performing simultaneous optimisation and HI. On the basis of this combined superstructure, an MINLP model with tight bounds on the variables is developed and implemented for its solution in the General Algebraic Modeling System (GAMS). The model is solved using a two-step solution strategy. The proposed model enables to explore simultaneously all interconnections within the proposed superstructure in order to find the configuration with the optimal trade-offs between capital and energy costs as demonstrated in this paper for different cases of a milk concentration process.

Reversible Supracolloidal Self‐Assembly of Cobalt Nanoparticles to Hollow Capsids and Their Superstructures

AbstractThe synthesis and spontaneous, reversible supracolloidal hydrogen bond‐driven self‐assembly of cobalt nanoparticles (CoNPs) into hollow shell‐like capsids and their directed assembly to higher order superstructures is presented. CoNPs and capsids form in one step upon mixing dicobalt octacarbonyl (Co2CO8) and p‐aminobenzoic acid (pABA) in 1,2‐dichlorobenzene using heating‐up synthesis without additional catalysts or stabilizers. This leads to pABA capped CoNPs (core ca. 5 nm) with a narrow size distribution. They spontaneously assemble into tunable spherical capsids (d≈50–200 nm) with a few‐layered shells, as driven by inter‐nanoparticle hydrogen bonds thus warranting supracolloidal self‐assembly. The capsids can be reversibly disassembled and reassembled by controlling the hydrogen bonds upon heating or solvent exchanges. The superparamagnetic nature of CoNPs allows magnetic‐field‐directed self‐assembly of capsids to capsid chains due to an interplay of induced dipoles and inter‐capsid hydrogen bonds. Finally, self‐assembly on air–water interface furnishes lightweight colloidal framework films.

Reversible Supracolloidal Self-Assembly of Cobalt Nanoparticles to Hollow Capsids and Their Superstructures.

The synthesis and spontaneous, reversible supracolloidal hydrogen bond-driven self-assembly of cobalt nanoparticles (CoNPs) into hollow shell-like capsids and their directed assembly to higher order superstructures is presented. CoNPs and capsids form in one step upon mixing dicobalt octacarbonyl (Co2 CO8 ) and p-aminobenzoic acid (pABA) in 1,2-dichlorobenzene using heating-up synthesis without additional catalysts or stabilizers. This leads to pABA capped CoNPs (core ca. 5 nm) with a narrow size distribution. They spontaneously assemble into tunable spherical capsids (d≈50-200 nm) with a few-layered shells, as driven by inter-nanoparticle hydrogen bonds thus warranting supracolloidal self-assembly. The capsids can be reversibly disassembled and reassembled by controlling the hydrogen bonds upon heating or solvent exchanges. The superparamagnetic nature of CoNPs allows magnetic-field-directed self-assembly of capsids to capsid chains due to an interplay of induced dipoles and inter-capsid hydrogen bonds. Finally, self-assembly on air-water interface furnishes lightweight colloidal framework films.

The Root and Nothing but the Root: Primary Compounds in Dutch

AbstractThis article is an addendum to recent contributions on the structure of compounds in root‐based frameworks, such as the Exoskeletal Model (Borer , :chap. 6, 2013b) or Distributed Morphology (Harley ). It presents a subtype of Dutch primary compounds of which the nonhead is demonstrably a bare root. The nonhead of this type of compounding is fully acategorial. It does not contain categorial heads (i.e., little heads) and neither is it categorized otherwise. As such, the discussion substantiates the root hypothesis (Halle & Marantz ; Borer ,b, ) and supports the view that the root does not need to be licensed by superstructure in order to be interpretable or realizable (see Alexiadou & Lohndal , pace Arad , Marantz , Ramchand , Starke ).

Evaluation of dynamic and impact wheel load factors and their application in design processes

A sustained increase in heavy axle loads and cumulative freight tonnages, coupled with increased development of high-speed passenger rail, is placing an increasing demand on railway infrastructures. Some of the most-critical areas of the infrastructure in need of further research are track components used in high-speed passenger, heavy haul and shared infrastructure applications. In North America, many design guidelines for these systems use historical wheel loads and design factors that may not necessarily be representative of the loading currently experienced on rail networks. Without a clear understanding of the nature of these loads and how design processes reflect them, it is impossible to adequately evaluate the superstructure in order to make design improvements. Therefore, researchers at the University of Illinois at Urbana-Champaign are conducting research to lay the groundwork for an improved and thorough understanding of the loading environment imparted into the track structure using wheel loads captured by wheel impact load detectors. This paper identifies several design factors that have been developed internationally, and evaluates their effectiveness based on wheel loads using several existing and new evaluative metrics. New design factors are also developed to represent the wheel-loading environment in a different manner. An evaluative approach to historical and innovative design methodologies will provide improvements to designs, based on actual loading experienced on today’s rail networks.

Three-Dimensional Self Assembly of Semiconducting Colloidal Nanocrystals: From Fundamental Forces to Collective Optical Properties.

Self-assembly of colloidal nanoparticles into higher order superstructures is becoming an important topic in current research in nanoscience. More and more research efforts are being dedicated to the controlled processing of nanoparticle dispersions to yield complex architectures from these simple building blocks. This is due to the fact that collective effects can emerge from an assembly of organized nanoparticles. Semiconducting colloidal nanocrystals such as quantum dots are promising materials for a wide range of applications in optoelectronic photovoltaics. The fundamental interactions that dictate the self-assembly of semiconducting colloidal nanocrystals in apolar solvents are reviewed with a focus on 3D structures and basic shapes (spheres, rods, and platelets). Emergent collective properties and the effect of the self-assembly on the optical properties of the particles are also discussed.

Change and Continuity in Europe and the Mediterranean around 1600bc

Based on recent evidence from both archaeological and natural sciences, in this paper we would like to sketch a historical geography of Europe and the Mediterranean around the year 1600bcand then discuss the changes observed during the 16th centurybcin relation to a possible correspondence with the Thera eruption. Our point of departure will be the sequence of events that took place during the months and years just before, during, and immediately after the Thera eruption. The available archaeological evidence permits us to explore the response of the local and regional communities, the logistics that were mobilised, and the political decisions adopted in light of these events. From this local and regional scenario we will move on to discuss the changes occurring in Europe, the Mediterranean, and the Near East during the 16th centurybc. At least four different socio-economic and political scenarios can be sketched, showing that the responses of Bronze Age societies were highly variable. At that point, we can ask how different political structures existing at the time reacted or were affected by the ecological and/or social dynamics. Basically, our itinerary concludes that the Thera eruption did not cause a severe climatic or environmental change, but touched the ideological realm particularly of those socio-political entities which were more dependent on complex ideological superstructures in order to legitimate extreme economic exploitation.

Effective Synthesis and Optimization Framework for Integrated Water and Membrane Networks: A Focus on Reverse Osmosis Membranes

Strict environmental regulations and social pressures have created the need for water and energy minimization in the process industries. Therefore, this work looks at the incorporation of a detailed reverse osmosis network (RON) superstructure within a water network superstructure in order to simultaneously minimize water, energy, operation, and capital costs. The water network consists of water sources, water sinks, and RO units for the partial treatment of the contaminated water. An overall mixed-integer nonlinear programming framework is developed that simultaneously evaluates both water recycle–reuse and regeneration reuse–recycle opportunities. The solution obtained from optimization provides the optimal connections between various units in the network arrangement, size and types of RO units, booster pumps, as well as energy recovery turbines. The paper looks at four cases to highlight the importance of including a detailed regeneration network within the water network instead of the traditional “bla...

Образование в современной политической повестке дня

The article touches on the contradictions between the market model and the social and welfare models of the state which remain unresolved especially in the educational sphere both in the developed and developing and post-communist countries including Russia. The special object of analysis is the educational aspect of new liberal ideology in the Western Europe as like as the ideology of Republicans in the USA identified as neoconservatives and compassionate conservatives. The new ideological perspectives of evolution of education and some educational projects in the globalization era are also discussed. Globalization of education refers to the worldwide discussions, processes, and institutions affecting local educational practices and policies, first of all, the national school systems. Today, many nations choose to adopt policies from the global superstructures in order to compete in the global economy. There is a constant dynamic of interaction: global ideas about school practices interact with local school systems while, through mutual interaction, both the local and the global are changed.

Representation of Soil-Foundation Systems and Its Application to Shaking Table Tests by Constructing a Mechanical Interface

Experimental studies on the dynamic response of structures comprising soil-foundation systems require an appropriately constructed soil-foundation model below the superstructures in order to properly estimate structural responses. In most studies, applying a small scaling is necessary for constructing the entire structural system, since there is limited space on shaking tables. This constraint has been a hindrance in experimental studies. Thus this study proposes a mechanical interface (MI) that represents the impedance characteristics of a 3 × 5 pile group embedded in a layered soil medium. The MI is constructed on the basis of lumped parameter models with gyro-mass elements. This element is mechanically realized in the MI using a rotational mass in combination with coupling gears. The results show that the MI properly simulates the impedance functions with frequency-dependent oscillations, and shaking table tests using the MI for an inelastic structure are demonstrated.