Chemical Patterns Research Articles

Chemical optimization of siRNA for safe and efficient silencing of placental sFLT1

Preeclampsia (PE) is a rising, potentially lethal complication of pregnancy. PE is driven primarily by the overexpression of placental soluble fms-like tyrosine kinase 1 (sFLT1), a validated diagnostic and prognostic marker of the disease when normalized to placental growth factor (PlGF) levels. Injecting cholesterol-conjugated, fully modified, small interfering RNAs (siRNAs) targeting sFLT1 mRNA into pregnant mice or baboons reduces placental sFLT1 and ameliorates clinical signs of PE, providing a strong foundation for the development of a PE therapeutic. siRNA delivery, potency, and safety are dictated by conjugate chemistry, siRNA duplex structure, and chemical modification pattern. Here, we systematically evaluate these parameters and demonstrate that increasing 2′-O-methyl modifications and 5′ chemical stabilization and using sequence-specific duplex asymmetry and a phosphocholine-docosanoic acid conjugate enhance placental accumulation, silencing efficiency and safety of sFLT1-targeting siRNAs. The optimization strategy here provides a framework for the chemical optimization of siRNAs for PE as well as other targets and clinical indications.

Gamma-ray light curves and spectra of classical novae

ABSTRACT The nucleosynthesis in classical novae, in particular that of radioactive isotopes, is directly measurable by its γ-ray signature. Despite decades of observations, MeV γ-rays from novae have never been detected – neither individually at the time of the explosion, nor as a result of radioactive decay, nor the diffuse Galactic emission from the nova population. Thanks to recent developments in modelling of instrumental background for MeV telescopes such as INTEGRAL/SPI and Fermi/GBM, the prospects to finally detect these elusive transients are greatly enhanced. This demands for updated and refined models of γ-ray spectra and light curves of classical novae. In this work, we develop numerical models of nova explosions using sub- and near-Chandrasekhar CO white dwarfs as the progenitor. We study the parameter dependence of the explosions, their thermodynamics and energetics, as well as their chemical abundance patterns. We use a Monte Carlo radiative transfer code to compute γ-ray light curves and spectra, with a focus on the early time evolution. We compare our results to previous studies and find that the expected 511-keV-line flash at the time of the explosion is heavily suppressed, showing a maximum flux of only $10^{-9}\, \mathrm{ph\, cm^{-2}\, s^{-1}}$ and thus making it at least one million times fainter than estimated before. This finding would render it impossible for current MeV instruments to detect novae within the first day after the outburst. Nevertheless, our time-resolved spectra can be used for retrospective analyses of archival data, thereby improving the sensitivity of the instruments.

Assessment of Easily Accessible Spectroscopic Techniques Coupled with Multivariate Analysis for the Qualitative Characterization and Differentiation of Earth Pigments of Various Provenance

Natural minerals and earths with coloring properties have been widely used as artistic pigments since prehistoric times. Despite being extensively studied, the complex chemistry of earth pigments is still unsatisfactory described with respect to their mineralogical and structural variability and origin. In this study, a large group of earth pigments from various geographical locations was investigated using easily accessible spectroscopic techniques and multivariate analysis with the aim to identify distinctive mineralogical and chemical characteristics of natural pigment sources. Portable X-ray fluorescence (p-XRF), Fourier transform infrared spectroscopy (FTIR) and fiberoptic Raman spectroscopy were used for the elemental, molecular and structural characterization of the investigated pigments. Diagnostic spectral features and chemical patterns (fingerprints) were identified and discussed with respect to their geological sources. Due to the occurrence of similar accompanying minerals, it was observed that the differentiation of red and yellow ochers is more challenging compared to green, brown and black pigments. However, for some of the investigated pigments, the presence of certain accessory minerals and/or of certain chemical patterns can have diagnostic value. Principal component analysis (PCA) of the FTIR and XRF data matrices showed promising results in terms of geological attribution, highlighting a promising tool for provenance research. The results of the study demonstrate the potential benefits of this rapid and nondestructive approach for the characterization and differentiation of earth pigments with similar hues coming from different geological sources.

A novel air‐stable O3‐type layered oxide cathode material with low Ni content for sodium‐ion batteries

A novel O3-NaMn0.42Fe0.42Ni0.17O2 cathode material for sodium-ion batteries is synthesized, for the first time, by a co-precipitation method followed by solid-state reaction. The effect of Ni2+, Cu2+ and Ca2+ substitution for Mn4+ and Fe3+ on the structural stability, rate capability and cycling performance of the cathode material are examined. Chemical titration results and powder X-ray diffraction patterns indicate that the substitution of Ni2+, Cu2+ and Ca2+ for Fe3+ and Mn4+ can inhibit the reaction of Na+ ions in the structure of O3-NaMn0.33Fe0.33Ni0.21Cu0.08Ca0.04O2 with air. The Ni2+, Cu2+ and Ca2+-substituted O3-NaMn0.33Fe0.33Ni0.21Cu0.08Ca0.04O2 cathode material show a higher capacity and better cycling stability than that of O3-NaMn0.42Fe0.42Ni0.17O2, indicating that a small amount of Ni2+, Cu2+ and Ca2+ substitution can improve the structure/air stability and the electrochemical performance. When O3-NaMn0.33Fe0.33Ni0.21Cu0.08Ca0.04O2 cathode material is combined with the hard carbon anode, a full cell gives 220 Wh kg−1 energy density and 100% capacity retention after 56 charge/discharge cycles at 0.5C. The O3-NaMn0.33Fe0.33Ni0.21Cu0.08Ca0.04O2 can be thought of as a potential cathode active material to encourage progress toward sodium-ion battery commercialization due to the high industrial applicability of the synthesis process and good electrochemical performance. Prime Novelty Statement A novel O3-NaMn0.42Fe0.42Ni0.17O2 cathode material for sod um on batter es is synthesized for the first time by a co-precipitation method with subsequent solid-state reaction. The substitution of Ni2+, Cu2+ and Ca2+ for Fe3+ and Mn4+ improves the air stability and electrochemical performance of O3-NaMn0.33Fe0.33Ni0.21Cu0.08Ca0.04O2 cathode material. When O3-NaMn0.33Fe0.33Ni0.21Cu0.08Ca0.04O2 cathode material couples with the hard carbon anode, a full cell gives an energy density of 220 Wh kg−1 and the capacity retention of 100% after 56 charge/discharge cycles.

Mass spectrometry-based profiling and imaging strategy, a fit-for-purpose tool for unveiling the transformations of ginsenosides in Panax notoginseng during processing

BackgroundPanax notoginseng, a valuable medicinal plant, is traditionally used to treat trauma, body pain, and cardiovascular diseases in two clinical forms including raw (crude) and processed form. Processing-triggered compound transformation is responsible for the distinct bioactivity between raw and processed Panax notoginseng. Nevertheless, investigating the chemical diversity and dynamic transformation pattern of processed Panax notoginseng is challenging. MethodsA new approach, which integrates multi-components characterization, processing trajectory depiction, discovery of differential markers, transformation mechanism of metabolites, in situ spatial distribution and transformation of metabolites, was established to elucidate the role of processing on the holistic chemical transformations of Panax notoginseng (PN). ResultsIn this study, 136 ginsenosides (mainly rare ginsenosides) were identified or tentatively characterized and the temperature-dependent chemical variation trajectory was depicted via principal component analysis (PCA). Nineteen processing-associated markers were confirmed by orthogonal partial least squares-discriminant analysis (OPLS-DA). For the first time, the transformation pathway of ginsenosides during processing were elucidated by integrating the precursor ion scan (PIS) and mimic processing strategy that involves with deglycosylation, dehydration, hydration, acetylation, and isomerization. Results of mass spectrometry imaging (MSI) revealed the major ginsenosides M-Rb1, R1, Rg1, Rb1, Rd, and Re exhibited distinct spatial distribution pattern that are highly abundant in the xylem and showed a downward trend during processing. We firstly depicted the spatial distribution of processing-triggered rare ginsenosides (Rg3, Rk1, Rg5, etc.), and in situ transformation of ginsenosides was discovered in the process of steaming. Additionally, this variation trend was consistent with untargeted metabolomics results. ConclusionThis study comprehensively revealed chemical diversity and dynamic transformation pattern and depicted the spatial distribution of ginsenosides of PN during processing. It could provide a clue for the distinct bioactivities between raw and processed PN and elucidate the role of processing on the holistic chemical transformations of natural products, more importantly, the proposed strategy is valuable for the quality evaluation and control of the processing of natural product.

Tuning interfacial interactions for bottom‐up assembly of surface‐anchored metal‐organic frameworks to tailor film morphology and pattern surface features

AbstractSurface‐anchored metal‐organic frameworks (surMOFs) integrate nanoporous supramolecular MOF materials directly into architectures for applications such as gas storage, chemical sensing, and energy storage. Layer‐by‐layer solution‐phase deposition of the MOF‐14 components (1,3,5‐tris(4‐carboxyphenyl)benzene and copper (II) dimers, respectively) produces a porous and conformal film on carboxyl‐terminated self‐assembled monolayers (SAMs). In this research, the formation of ultrathin (less than 25 nm) surMOF films on codeposited bicomponent SAMs and microcontact printed SAMs is investigated by atomic force microscopy, ellipsometry, infrared spectroscopy, and contact angle goniometry. SAMs composed of methyl‐terminated alkanethiols assembled on gold substrates inhibit surMOF formation, whereas carboxyl‐terminated alkanethiols promote MOF‐14‐based film growth. To tune the density of carboxyl groups that anchor the film, methyl‐ and carboxyl‐terminated alkanethiols of varying concentrations are codeposited on gold. This systematic study demonstrates how surMOF film formation and morphology are impacted by these SAMs with mixed surface functionalities. Chemical patterning methods for SAMs, such as microcontact printing (μCP), commonly have mixed chemical functionalities within certain regions of the pattern. Insights gained regarding how mixed surface functionalities affect surMOF film formation are applied herein to optimize the μCP method to produce chemically patterned SAMs that selectively direct surMOF assembly to produce high‐quality surMOF film features.

Directing Multicellular Organization by Varying the Aspect Ratio of Soft Hydrogel Microwells (Adv. Sci. 17/2022)

Directing Multicellular Organization In article number 2104649, Lewis H. Romer, David H. Gracias, and co-workers report the discovery of an endothelial cell self-organization mechanism that is guided simply by tuning the aspect ratio of 3D geometry on soft hydrogel substrates. This mechanism is driven by a balance between intra- and extracellular interactions and is independent of protein or chemical patterning.

Unfolding the structural stability of nanoalloys via symmetry-constrained genetic algorithm and neural network potential

The structural stability of nanoalloys is a challenging research subject due to the complexity of size, shape, composition, and chemical ordering. The genetic algorithm is a popular global optimization method that can efficiently search for the ground-state nanoalloy structure. However, the algorithm suffers from three significant limitations: the efficiency and accuracy of the energy evaluator and the algorithm’s efficiency. Here we describe the construction of a neural network potential intended for rapid and accurate energy predictions of Pt-Ni nanoalloys of various sizes, shapes, and compositions. We further introduce a symmetry-constrained genetic algorithm that significantly improves the efficiency and viability of the algorithm for realistic size nanoalloys. The combination of the two allows us to explore the space of homotops and compositions of Pt-Ni nanoalloys consisting of up to 4033 atoms and quantitatively report the interplay of shape, size, and composition on the dominant chemical ordering patterns.

Authentication of craft and industrial beers by excitation-emission matrix fluorescence spectroscopy and chemometrics

In this article, some ingenious strategies based on chemometrics were proposed to achieve the authentication of industry and craft beers in the Chinese market. Excitation-emission matrix fluorescence spectroscopy technique was used to obtain high-dimensional data of beer samples with 3 dilution levels (the content of beer in water = 3%, 50% and 100%). Alternating trilinear decomposition (ATLD) and alternating quadrilinear decomposition (AQLD) algorithms were used to characterize beer samples. Three chemical pattern recognition methods including partial least squares-discrimination analysis (PLS-DA), principal component analysis-linear discriminant analysis (PCA-LDA) and random forest (RF) were used to handle two classification tasks with different aims, including the classification of industry beer and craft beer (Case 1) and the classification of industry beer and craft beers of different brands (Case 2). For case 1, the correct classification rates of the cross-validation, training set, test set and prediction set are all 100% obtained by the classification methods based on four-way data arrays. For case 2, the results obtained by PLS-DA based on four-way data are excellent, the correct classification rates of cross-validation, training set, test set and prediction set are 90.3%, 100.0%, 100% and 88.9%, respectively. This study showed that four-way data coupled with PLS-DA could be a good choice for all beer classification tasks. The proposed method is expected to safeguard the interests of consumers and manufacturers, and it can be extended to the authentication of other beverages.

Minimal Increments of Hydrophobic Collapse within the N-Terminus of the Neuropeptide Galanin.

The neuropeptide galanin has a 35-year history as an intriguing target in drug design owing to its implication as a potential anticonvulsant and neuronal trophic factor among many other therapeutically interesting functions including analgesia and mood alteration. In this study, we report the structural characterization of three synthetic fragments of the galanin N-terminus in buffered aqueous solution: hGal(2-12)KK, hGal(1-12)KK, and hGal(1-17)KK. High-field two-dimensional 1H-1H nuclear magnetic resonance (NMR) data were acquired for these fragments and used to derive distance restraints. We further utilized modified hydrogen bonding and dihedral restraints to reflect chemical shift patterns in the data, which revealed the signature of a weakly folded helix. Together, these sets of restraints were used to generate NMR structures of all three fragments, which depict a core of hydrophobic residues that cluster together regardless of the presence of a helical structure, and correspond to residues in the N-terminus of galanin that have been previously shown to be critical for binding its receptors. The helical structure only appears following the inclusion of Gly(1) in the sequence, and at longer sequence lengths, unlike many other peptides, the helix does not propagate. Rather, a few turns of poorly ordered helix appear to be a secondary consequence of clusters of hydrophobic sidechains that are conserved across all of the peptides in this study; the helices themselves appear ordered as a consequence of this clustering, and these clusters compare directly to those observed recently to make contacts between galanin and two of its receptor subtypes. Collapsed hydrophobic residues therefore organize and compose the functional core of human galanin and raise interesting questions about the nature of the conformational order in ligands that bind cell surface receptors.

Phytochemical content, especially spermidine derivatives, presenting antioxidant and antilipoxygenase activities in Thai bee pollens.

BackgroundBee pollen (BP) is full of useful nutrients and phytochemicals.Its chemical components and bioactivities depend mainly on the type of floral pollen.MethodsMonofloral BP from Camellia sinensis L., Mimosa diplotricha, Helianthus annuus L., Nelumbo nucifera, Xyris complanata, and Ageratum conyzoides were harvested. Crude extraction and partition were performed to yield solvent-partitioned extracts of each BP. Total phenolic content (TPC) was assayed by the Folin-Ciocalteu method, while the flavonoid content (FC) was measured by the aluminium chloride colorimetric method. Antioxidant capacity was measured by the (i) 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, (ii) 2,2’-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) scavenging activity and its Trolox equivalent antioxidant capacity (TEAC), and (iii) ferric reducing antioxidant power (FRAP). All samples were tested for lipoxygenase inhibitory (LOXI) activity. The most active sample was enriched by silica gel 60 column chromatography (SiG60-CC) and high performance liquid chromatography (HPLC), observing the chemical pattern of each fraction using thin layer chromatography. Chemical structure of the most active compound was analyzed by proton nuclear magnetic resonance and mass spectrometry.ResultsDichloromethane (DCM)-partitioned BP extracts of H. annuus L. and M. diplotricha (DCMMBP) showed a very high TPC, while DCMMBP had the highest FC. In addition, DCMMBP had the strongest DPPH and ABTS radical scavenging activities (as a TEAC value), as well as FRAP value. Also, DCMMBP (60 µg/mL) gave the highest LOXI activity (78.60 ± 2.81%). Hence, DCMMBP was chosen for further enrichment by SiG60-CC and HPLC. Following this, the most active fraction showed higher antioxidant andLOXI activities with an EC50 for DPPH and ABTS of 54.66 ± 3.45 µg/mL and 24.56 ± 2.99 µg/mL (with a TEAC value of 2,529.69 ± 142.16 µmole TE/g), respectively, and a FRAP value of 3,466.17 ± 81.30 µmole Fe2+/g and an IC50 for LOXI activity of 12.11 ± 0.36 µg/mL. Triferuloyl spermidines were revealed to be the likely main active components.ConclusionsTPC, FC, and spermidine derivatives played an important role in the antioxidant and antilipoxygenase activities in M. diplotricha bee pollen.

Archimedean Spirals Form at Low Flow Rates in Confined Chemical Gardens.

We describe and study the formation of confined chemical garden patterns. At low flow rates of injection of cobalt chloride solution into a Hele-Shaw cell filled with sodium silicate, the precipitate forms with a thin filament wrapping around an expanding “candy floss” structure. The result is the formation of an Archimedean spiral structure. We model the growth of the structure mathematically. We estimate the effective density of the precipitate and calculate the membrane permeability. We set the results within the context of recent experimental and modeling work on confined chemical garden filaments.

Out-of-equilibrium chemical logic systems: Light- and sound-controlled programmable spatiotemporal patterns and mechanical functions

<h2>Summary</h2> Living systems at different scales function through the sensing of multiple external signal inputs, which are further processed based on binary or more complicated computational models and networks. Inspired by such behavior, here, we show that the information processing in out-of-equilibrium chemical systems utilizing binary Boolean logic can be exploited to obtain transient functions such as spatiotemporally controlled chemical gradients and patterns in response to specific combination of multiple physical or chemical inputs (light, audible sound, and O₂). We further explore systems that are able to execute highly complicated functions such as guiding a cargo through a maze by processing the information from multiple external stimuli. Our approach of integrating and encoding binary Boolean logic within out-of-equilibrium chemical systems for the extraction of mechanical work to execute transient biomimicking functions can expand the realms of systems chemistry and related research and help us design smart materials.

Extended-range Variable Altitude Balloons for Venus atmospheric missions

In-situ exploration of Venus is challenging due to its severe environment, which is benign (∼25 °C and 1 bar) at an altitude of 55 km, but rapidly becomes hostile at lower altitudes. The temperature increases to ∼465 °C, and pressure reaches 90 bars at the surface. These conditions have limited in-situ missions to high altitude balloons at 55 km that survived only 48 h. High-altitude balloon missions are stymied by the opaqueness of the Venusian clouds and constant altitude. Long-duration, extended range variable-altitude balloons covering below the clouds could enhance the science capabilities of the missions by measuring chemical species, isotopes and atmospheric flow patterns in and underneath the clouds. A new energy storage system tolerant to the high temperatures at low altitudes is needed to support such a balloon. A novel variable altitude balloon architecture with an extended range of 55–20 km (VAB-X) was developed under the NASA Innovative and Advanced Concepts (NIAC) program and is described here. The architecture comprises a high-temperature tolerant balloon and photovoltaic array for providing spacecraft power, a reversible solid oxide fuel (SOFC) for low-altitude power and fuel regeneration, and reversible metal hydride (MH) for hydrogen storage. Hydrogen is used for the buoyancy and altitude control of the zero-pressure balloon and as fuel for SOFC. Water brought from Earth can replenish the hydrogen lost to leaks during the mission. Preliminary analyses reveal the efficacy of the architecture for long-term Venus exploration over 55-20 km altitude, with a high proportion (∼20%) of the total suspended mass (>20 kg) available for science payload.

The hydrothermal footprint of the Crixás deposit: New vectors for orogenic gold exploration in central Brazil

The main gold deposits of the Archaean-Paleoproterozoic Terrain of Goiás, in central Brazil, occur in the Crixás Greenstone Belt, one of the five volcanosedimentary sequences of this terrain. The Crixás orogenic gold deposit consists of several orebodies structurally controlled by low to moderate angle thrust faults, hosted in different stratigraphic units that exhibit contrasting mineralization styles and hydrothermal alteration assemblages.This study characterizes the hydrothermal footprints of the Palmeiras Structure and Structure IV, which control the orebodies hosted in the hydrothermally-altered mafic metavolcanic rocks and carbonaceous schists, respectively. We assessed the magnitude of fluid-rock interactions by integrating mineralogical, geochemical, and petrophysical data with the reflectance spectroscopy results for drill core samples for both structures.The Palmeiras Structure hydrothermal footprint is characterized by a distal halo composed of Fe-Mg chlorite + biotite ± carbonates (calcite and Fe dolomite), followed by the intermediate halo defined by epidote + carbonates (dolomite, Fe dolomite, and ankerite) ± Fe-Mg chlorite, and proximal halo composed of muscovite + Fe-enriched chlorite ± paragonite, magnetite, tourmaline, Fe dolomite, and ankerite. Additionally, the chemical pattern of the hydrothermal alteration along the Palmeiras Structure has significantly increased concentrations of alkali (K2O, Na2O, Rb, Cs, Li, and Ba), as well as Fe2O3, Al2O3, TiO2, LOI, U, W, Th, and Ta towards the gold mineralization. Also, the high magnetite concentration resulted in high magnetic susceptibility and density, with values above 1432.00×10–3 SI. In Structure IV, the proximal alteration assemblage comprises muscovite + Fe dolomite, Fe-Mg chlorite + arsenopyrite. The lithogeochemical signature is characterized by enrichment in SiO2, CaO, Na2O, K2O, P, Ba, and pathfinder elements As, W, Sb, Te, that increase towards the gold mineralization. A new potential target hosted in the hydrothermalized metabasalt was identified, whose signature is defined by the occurrence of muscovite, chlorite and enrichment in K2O, Ba, Rb, Li Cs and pathfinder elements such as As, W, Sb, Te.This study demonstrates that the integrated application of reflectance spectroscopy, petrophysics and chemical analyses provide a powerful tool for characterizing the hydrothermal footprint and determining the vectors toward gold mineralization in regional-scale mineral exploration.

Aquifer system and depth specific chemical patterns in fractured-rock groundwater from the Critical Zone revealed by untargeted LC-MS-based metabolomics

In the Earth's Critical Zone, water plays an essential role as a collector and transporter of metabolites and their transformation products. It is generally believed that the chemical profiles of groundwater are strongly impacted by land use. However, predictors for the effects of above-ground natural and anthropogenic activities on below-ground chemistry are rare. We reasoned that comparing groundwater metabolomes from different land-use sites and depths can give insight into this coupling of above and below-ground processes in the Critical Zone. This study used an LC-MS-based untargeted metabolomic approach to identify links between groundwater metabolomes from monitoring wells in fractured carbonate-/siliciclastic alternations along a hillslope of the Hainich Critical Zone Exploratory (CZE) in Thuringia, Germany. Our results identify the land-use type, aquifer system, and sampling depth as critical factors determining the differences among groundwater metabolomes. We established five groundwater metabolic clusters and correlated these to the aquifer systems, hydrogeochemistry, and microbial community composition. Our untargeted metabolomic approach reveals the limited connectivity of groundwater chemical profiles with above-ground activities and illustrates how deep the input signals can travel.

Stamping colors with solid-state superionic stamping (S4)

Traditional top-down approaches to producing metallic nanostructures are usually indirect; involve ultra-high vacuum processing steps and deep sub-micron lithography such as electron-beam lithography (EBL). Therefore, such pathways are difficult to scale up to high production rates. Additionally, they are too expensive to deploy in the production of single-use, low-cost products like plasmonic biological or chemical sensors, security tags or decorative patterns, all of which involve metallic nanopatterns. Hence, there is a need for more scalable and affordable manufacturing pathways for producing metallic nanostructures. In this work, we demonstrate a scalable manufacturing pathway for patterning silver nanostructures for plasmonic color generation. The pathway begins with the production of a single master pattern. We use commercially available Two-Photon Lithography (TPL) to direct-write a mask on a silicon substrate. Shallow etching of the silicon substrate with this mask by the Reactive Ion Etching (RIE) process (or Deep Reactive-Ion Etching for deeper patterns) produces a silicon master mold with the desired pattern. This master is used for hot embossing AgI-AgPO3 glass, a chemically stable, pure Ag-ion conductor with a low glass transition temperature (of about 100 °C, depending on its stoichiometry), into a stamp. This glass stamp, in turn, is used in the Solid-State Superionic Stamping (S4) process to electrochemically imprint the desired pattern into several substrates. Here, with this direct, facile, and efficient process, we report that a single nano-patterned stamp is capable of producing several high-fidelity replicas of the master.

Detection of Inhomogeneity After Mixing Solutions by Analyzing the Chemical Wave Pattern in the Belousov-Zhabotinsky Reaction

The correlation between BZ reaction and mixing state has been studied for decades, and the researchers are trying to apply it to chemical engineering. We observed a chemical wave pattern in the Belouzov-Zhabotinsky (BZ) reaction based on the inhomogeneity after mixing BZ and ferroin solutions with a mixing method named the rotation-and-stop method. A one-dimensional chemical wave appeared for large inhomogeneity in mixing. The frequency and wavenumber decreased with decreasing degree of inhomogeneity. In an almost perfectly mixed state, the wavenumber significantly reduced and approached the global oscillation. The degree of mixing could be efficiently determined by this reported method. Perfect mixing has never been realized in natural and biological systems. The results of this study can be applied to estimate the degree of mixing in a solution that is not being stirred after the mixing process.

Cascade reaction networks within audible sound induced transient domains in a solution

Spatiotemporal control of chemical cascade reactions within compartmentalized domains is one of the difficult challenges to achieve. To implement such control, scientists have been working on the development of various artificial compartmentalized systems such as liposomes, vesicles, polymersomes, etc. Although a considerable amount of progress has been made in this direction, one still needs to develop alternative strategies for controlling cascade reaction networks within spatiotemporally controlled domains in a solution, which remains a non-trivial issue. Herein, we present the utilization of audible sound induced liquid vibrations for the generation of transient domains in an aqueous medium, which can be used for the control of cascade chemical reactions in a spatiotemporal fashion. This approach gives us access to highly reproducible spatiotemporal chemical gradients and patterns, in situ growth and aggregation of gold nanoparticles at predetermined locations or domains formed in a solution. Our strategy also gives us access to nanoparticle patterned hydrogels and their applications for region specific cell growth.

Engineering the domain roughness of block copolymer in directed self-assembly

The influence of line width roughness (LWR) and line edge roughness (LER) on the reliability and performance of transistors becomes more and more important in the semiconductor fabrication as the critical dimension continues shrinking. Directed self-assembly of block copolymers (DSA of BCPs) is a potential solution for next generation lithography, however, it still lacks research on the influencing factors of LER and LWR in DSA. Here we investigate the effect of the molecular weight distribution ( Ɖ ), normalized pattern period ( L S / L O ), pattern duty cycle (W/ L S ) and annealing time on the LER and LWR of domain boundaries in assembled poly(styrene- block -methyl methacrylate) (PS- b -PMMA) films on chemical patterns. The assembly kinetics is faster when the Ɖ of PS- b -PMMA is larger, while the Ɖ of PS- b -PMMA does not affect the L S / L O window for defect-free assembly when the annealing time is sufficient. Ɖ is the most critical parameter to control LER and LWR, and both increase with the increase of Ɖ on chemical patterns with same L S / L O . Besides Ɖ , L S / L O also plays an important role in the control of LER and LWR and the roughness increases with the increase of L S / L O . In addition, the annealing time and W/ L S of chemical pattern have little effect on LER and LWR. This will provide insight to engineer LER and LWR of block copolymer domains in DSA. • LER and LWR in PS-b-PMMA films are determined by Ɖ of PS- b -PMMA. • The annealing time and the duty cycle of chemical patterns have little effect on LER and LWR. • A shorter annealing time is needed for defect-free assembly for BCPs with broader Ɖ s. • The mechanism is revealed for increased LER and LWR in BCPs with broader Ɖ s.