Chemical Patterns Research Articles

Noninvasive Detection of Skin Cancer by Imprint Desorption Electrospray Ionization Mass Spectrometry Imaging.

We report a technique for the noninvasive detection of skin cancer by imprint desorption electrospray ionization mass spectrometry imaging (DESI-MSI) using a transfer agent that is pressed against the tissue of interest. By noninvasively pressing a tape strip against human skin, metabolites, fatty acids, and lipids on the skin surface are transferred to the tape with little spatial distortion. Running DESI-MSI on the tape strip provides chemical images of the molecules on the skin surface, which are valuable for distinguishing cancer from healthy skin. Chemical components of the tissue imprint on the tape strip and the original basal cell carcinoma (BCC) section from the mass spectra show high consistency. By comparing MS images (about 150-μm resolution) of same molecules from the tape strip and from the BCC section, we confirm that chemical patterns are successfully transferred to the tape stripe. We also used the technique to distinguish cherry angiomas from normal human skin by comparing the molecular patterns from a tape strip. These results demonstrate the potential of the imprint DESI-MSI technique for the noninvasive detection of skin cancers as well as other skin diseases before and during clinical surgery.

Chemical Composition and Genome Pattern as a Means of Identifying the Origin of Preserved Wild Garlic (Allium ursinum L.) in Poland

In Poland, the mountainous and hilly regions until recently were territories with unbalanced and poor diet quality, especially in early spring. Wild edible plants were or remain influential in supplementing a human diet. One of the earliest wild edible plants to appear in the growing season, characteristic of a broad swath of Europe from Ukraine to Germany, remains wild (ramsons) garlic (Allium ursinum L.). This paper assesses the impact of the vegetation site and preservation methods on the content of chlorophylls, β-carotene, vitamin C, total polyphenols, and antioxidant activity (ABTS, DPPH, and FRAP) of wild garlic leaves. In addition, the connection between its genome pattern and chemical composition was assessed. The plants were collected in three locations in the Carpathian foothills, and the reference sample was plants collected in the lowlands. The site from which the raw material was harvested has a statistically significant effect on the chemical composition of the preserved leaves of wild garlic. The profiles of the analysed components differed in the material from a different site. Wild garlic leaves from mountainous areas (400–600 m above sea level) were characterized by a higher content of the analysed ingredients than leaves obtained from lowland sites (200 m above sea level). Moreover, the material from the lowlands had a different genetic pattern from the leaves from the mountainous areas.

A strontium-rich ultra-metal-poor star in the Atari disc component

ABSTRACT We report on the discovery of the first ultra-metal-poor (UMP) star 2MASS J20500194−6613298 (J2050−6613; [Fe/H] = −4.05) selected from the Gaia BP/RP spectral catalogue that belongs to the ancient Atari disc component. We obtained a high-resolution spectrum for the star with the MIKE spectrograph on the Magellan-Clay telescope. J2050−6613 displays a typical chemical abundance pattern for UMP stars, including carbon and zinc enhancements. In contrast, J2050−6613 shows extremely high [Sr/Fe] and [Sr/Ba] ratios compared to other stars in the [Fe/H] < −4.0 regime. J2050−6613 is most likely an early Population II star that formed from a gas cloud that was chemically enriched by a massive Population III hypernova (E > 1052 erg). Such a Population III core-collapse hypernova could simultaneously explain the origin of the abundance pattern of light and heavy elements of 2MASS J2050−6613 if a large amount of Sr of ∼10−5 M⊙ was produced, possibly by neutrino-driven (wind) ejecta. Therefore, the abundance pattern of 2MASS J2050−6613 places important constraints on Sr-producing nucleosynthesis sources operating in the Atari progenitor at the earliest times.

Multi-phase quantitative compositional mapping by LA-ICP-MS: Analytical approach and data reduction protocol implemented in XMapTools

Mapping of trace element signatures is an expanding tool in geoscience and material sciences, which allows the study of solid materials, and processes that may not be captured by major elements. Developments in laser-ablation inductively-coupled-plasma mass-spectrometry (LA-ICP-MS) capabilities in the last decade now provide the necessary spatial resolution for in situ element mapping. The acquisition of two-dimensional, fully quantitative and geologically meaningful data with LA-ICP-MS is still a challenging task, and a particular obstacle is the calibration of inhomogeneous phases, such as chemically zoned minerals. This work presents a novel approach to data reduction and image generation for multi-element mapping employing LA-ICP- quadrupole MS (LA-ICP-QMS), implemented in the free and open-source software XMapTools. Three geological applications are presented to illustrate the benefits of the procedures. Garnet from an eclogitic sample (Lato Hills, Togo) and plagioclase, K-feldspar, biotite from a migmatite sample (El Oro Complex, Ecuador) were mapped multiple times at different spatial resolutions to test the calibration quality and chemical detection capabilities. Rutile in a metapelite sample (Val Malenco, Italian Alps) was mapped, and Zr-in-rutile thermometry shows a temperature range of 510 to 550 °C within a single grain. The accuracy of the LA-ICP-MS method was verified by comparison with zoned major and minor element maps (garnet, plagioclase) and Ti-in-biotite geothermometry maps obtained by electron probe microanalysis (EPMA). A spatial resolution of up to 5 μm is achieved with LA-ICP-QMS, which is similar to the resolution reported for LA-ICP time-of-flight mass spectrometry (LA-ICP-TOFMS), albeit at significantly lower acquisition speed. Maps with lower spatial resolution offer better chemical detection power as demonstrated by lower per-pixel limit of detection (LOD) map calculation. Moreover, such maps are also recorded faster. The pixel allocation strategy and the instrumental conditions also have a direct impact on map quality. We recommend that maps are interpolated to square pixels, where a pixel consists of multiple sweeps to gain an improved detection power. Benchmarks using an emulated LA-ICP-MS mapping show that the spot size, together with scan direction, can lead to a shift in composition depending on the feature size of chemical patterns. This is verified by mapping a thin 10 μm annulus in garnet visible in REE and such compositional shifts can have a significant impact on e.g., diffusion modelling. The new software solution provides a multi-standard and variable composition calibration of LA-ICP-MS maps with single pixel LOD filtering at 95% confidence, allowing the user to quantify inhomogeneous materials of major and trace elements simultaneously with improved accuracy.

The Polyperfluoromethylisopropyl Ether used as a surface tensiometry tool for non-invasive quality assessment of peloids (TVS mud index®): An overview

Background Surface tensiometry consented to characterize the surface free energy of geomaterials in an integrated and non-destructive way. A new surface tensiometry tool, based on the contact angle measurement of Polyperfluoromethylisopropyl Ether (TVS mud index), has thus developed in the early 2000s. The TVS mud index was for the first time employed from 2005 to 2010 for surface tensiometry characterization of peloids for pelotherapy from Abano Terme and Montegrotto Terme (Pa-dova, Italy). We aim to report the surface tensiometry application in the thermal field, and show the potentialities of TVS mud index as a marker for the non invasive quality control of the peloids and their maturation process. Methods The determination of the typical chemical-mineralogical characteristics of a Euganean Thermal Mud (ETM) and their surface tensiometry allowed us to demonstrate the link between the chemical data from X-ray fluorescence (XRF) analysis and they performed using a tensiometer to assess the quality of the peloid and its biological maturation process. Results The liquid test Polyperfluoromethylisopropyl Ether-based demonstrated the link between variations in volume elements and surface free energy of muddy matrices. The research results here showed that the TVS mud index is linked to the chemical pattern of peloids. Conclusions The research work implemented in the period 2005-2010 showed the potentialities of surface tensiometry in the assessment of peloids for pelotherapy using Polyperfluoromethylisopropyl Ether as a liquid test.

Evolution and chemical diversity of the volatile compounds in Salvia species.

The plant essential oils are composed of volatile compounds and have significant value in preventing and treating neurological diseases, anxiety, depression, among others. The genus Salvia has been shown to be an important medicinal resource, especially the aerial parts of genus Salvia, which are rich in volatile compounds; however, the chemical diversity and distribution patterns of volatile compounds in Salvia species are still unknown. The work is performed to analyse the chemical diversity and distribution patterns of volatile compounds in genus Salvia. The genomic single nucleotide polymorphisms (SNPs) combined with gas chromatography-mass spectrometry (GC-MS) were used to explore the evolution and chemical diversity of Salvia volatile compounds. Initially, the genetic relationship of genus Salvia was revealed by phylogenetic tree that was constructed based on SNPs. And then, GC-MS was applied to explore the chemical diversity of volatile compounds. The results indicated that the volatile compounds were mainly monoterpenoids, sesquiterpenoids, and aliphatic compounds. The genomic SNPs divided species involved in this work into four branches. The volatile compounds in the first and second branches were mainly sesquiterpenoids and monoterpenoids, respectively. Species in the third branch contained more aliphatic compounds and sesquiterpenoids. And those in the fourth branch were also rich in monoterpenoids but had relatively simple chemical compositions. This study offered new insights into the phylogenetic relationships besides chemistry diversity and distribution pattern of volatile compounds of genus Salvia, providing theoretical guidance for the investigations and development of secondary metabolites.

ÆSOPUS 2.0: Low-temperature Opacities with Solid Grains

Abstract In this study we compute the equation of state and Rosseland mean opacity from temperatures of T ≃ 30,000 K down to T ≃ 400 K, pushing the capabilities of the ÆSOPUS code into the regime where solid grains can form. The GGchem code is used to solve the chemistry for temperatures less than ≃3000 K. Atoms, molecules, and dust grains in thermodynamic equilibrium are all included in the equation of state. To incorporate monochromatic atomic and molecular cross sections, an optimized opacity sampling technique is used. The Mie theory is employed to calculate the opacity of 43 grain species. Tables of Rosseland mean opacities for scaled-solar compositions are provided. Based on our computing resources, opacities for other chemical patterns, as well as various grain sizes, porosities, and shapes, can be easily computed upon user request to the corresponding author.

Chemical Patterning on Nanocarbons: Functionality Typewriting.

Nanocarbon materials have become extraordinarily compelling for their significant potential in the cutting-edge science and technology. These materials exhibit exceptional physicochemical properties due to their distinctive low-dimensional structures and tailored surface characteristics. An attractive direction at the forefront of this field involves the spatially resolved chemical functionalization of a diverse range of nanocarbons, encompassing carbon nanotubes, graphene, and a myriad of derivative structures. In tandem with the technological leaps in lithography, these endeavors have fostered the creation of a novel class of nanocarbon materials with finely tunable physical and chemical attributes, and programmable multi-functionalities, paving the way for new applications in fields such as nanoelectronics, sensing, photonics, and quantum technologies. Our review examines the swift and dynamic advancements in nanocarbon chemical patterning. Key breakthroughs and future opportunities are highlighted. This review not only provides an in-depth understanding of this fast-paced field but also helps to catalyze the rational design of advanced next-generation nanocarbon-based materials and devices.

Nonsaturating Linear Magnetoresistance Manifesting Two-Dimensional Transport in Wet-Chemical Patternable Bi2O2Te Thin Films.

Two-dimensional (2D) materials with exotic transport behaviors have attracted extensive interest in microelectronics and condensed matter physics, while scaled-up 2D thin films compatible with the efficient wet-chemical etching process represent realistic advancement toward new-generation integrated functional devices. Here, thickness-controllable growth and chemical patterning of high-quality Bi2O2Te continuous films are demonstrated. Noticeably, except for an ultrahigh mobility (∼45074 cm2 V-1 s-1 at 2 K) and obvious Shubnikov-de Hass quantum oscillations, a 2D transport channel and large linear magnetoresistance are revealed in the patterned Bi2O2Te films. Investigation implies that the linear magnetoresistance correlates with the inhomogeneity described by P. B. Littlewood's theory and EMT-RRN theory developed recently. These results not only reveal the nonsaturating linear magnetoresistance in high-quality Bi2O2Te but shed light on understanding the corresponding physical origin of linear magnetoresistance in 2D high-mobility semiconductors and providing a pathway for the potential application in multifunctional electronic devices.

Anisotropic Wettability Induced by Femtosecond Laser Ablation

Laser ablation has been utilized for locally and selectively modifying the surface wettability of materials in situ and enabling on‐demand microfabrication. The anisotropic wettability has been observed on chemical and/or topographical patterns, such as an array of laser‐inscribed strips with spacings, created on surfaces during the fabrication process. Herein, the effectiveness of the femtosecond laser ablation is evaluated in selectively modifying surface wettability. The areas processed by laser ablation exhibit anisotropic wetting behavior, even after the laser strips are overlapped. The laser‐induced anisotropic surface wettability is present in space governed by laser scanning speed, scan/strip overlap, laser fluence, scan repetition, and bidirectional scanning angle. Moreover, the femtosecond laser ablation process is optimized to enhance the conventional laser inscription, leading to a modified and consistent methodology to achieve cost‐effective fabrication.

Chemical characteristics, distribution patterns, and source apportionment of particulate elements and inorganic ions in snowpack in Harbin, China

Snowpack, which serves as a natural archive of atmospheric deposition of multiple pollutants, is a practical environmental media that can be used for assessing atmospheric records and input of the pollutants to the surface environments and ecosystems. A total of 29 snowpack samples were collected at 20 sampling sites covering three different functional areas of a major city (Harbin) in Northeast China. Two samples at the “snow layer” and one or two samples at the “particulate layer” were collected at each sampling site in the industrial areas characterized by multi-layer snowpack, and only one sample at the “snow layer” was collected at each sampling site in the cultural and recreational as well as agricultural areas. The snow contents of 31 elements (Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Y, Cd, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Pb) and six major water-soluble inorganic ions (WSIIs, NH4+, K+, Ca2+, NO2−, NO3−, and SO42−) were analyzed. The total mass of the measured elements is dominated (95.8%–99.2%) by crustal elements. Heavy metals only account for 0.77%–4.07% of the total mass of the elements, but are occasionally close to or even above the standard limit in the “Environmental Quality Standards for Surface Water” of China (GB3838-2002). SO42− and Ca2+ are the main anion and cation, accounting for 34.9%–81.1% and 1.43%–29.9%, respectively, of the measured total ions. Total atmospheric deposition of crustal elements and heavy metals is dominated by wet deposition in areas near the petrochemical plant and by dry deposition in areas near the cement plant. Coal combustion, industrial emissions, and traffic-related activities lead to the enrichment of heavy metals in the snowpacks of urban and suburban areas, while coal combustion and biomass burning contribute to pollution in rural areas. The cities and regions situated in the western, northwestern, northern, and northeastern directions from Harbin are potential source regions of these pollutant species.

Chemo-dynamical tagging in the outskirts: The origins of stellar substructures in the Magellanic Clouds

We present the first detailed chemical analysis from APOGEE-2S observations of stars in six regions of recently discovered substructures in the outskirts of the Magellanic Clouds extending to 20° from the Large Magellanic Cloud (LMC) center. We also present, for the first time, the metallicity and α-abundance radial gradients of the LMC and the Small Magellanic Cloud (SMC) out to 11° and 6°, respectively. Our chemical tagging includes 13 species including light, α-, and Fe-peak elements. We find that the abundances of all of these chemical elements in stars populating two regions in the northern periphery, along the northern “stream-like” feature, show good agreement with the chemical patterns of the LMC, and thus likely have an LMC origin. For substructures located in the southern periphery of the LMC we find more complex chemical and kinematical signatures, indicative of a mix of LMC-like and SMC-like populations. The southern region closest to the LMC shows better agreement with the LMC, whereas that closest to the SMC shows a much better agreement with the SMC chemical pattern. When combining this information with 3D kinematical information for these stars, we conclude that the southern region closest to the LMC likely has an LMC origin, whereas that closest to the SMC has an SMC origin and the other two southern regions have a mix of LMC and SMC origins. Our results add to the evidence that the southern substructures of the LMC periphery are the product of close interactions between the LMC and SMC, and thus likely hold important clues that can constrain models of their detailed dynamical histories.

GC-MS Fingerprinting Combined with Chemical Pattern-Recognition Analysis Reveals Novel Chemical Markers of the Medicinal Seahorse

Seahorse is a valuable marine-animal drug widely used in traditional Chinese medicine (TCM), and which was first documented in the “Ben Cao Jing Ji Zhu” during the Liang Dynasty. Hippocampus kelloggi (HK) is the most common seahorse species in the medicinal material market and is one of the genuine sources of medicinal seahorse documented in the Chinese pharmacopeia. It is mainly cultivated in the Shandong, Fujian, and Guangxi Provinces in China. However, pseudo-HK, represented by Hippocampus ingens (HI) due to its similar appearance and traits, is often found in the market, compromising the safety and efficacy of clinical use. Currently, there is a lack of reliable methods for identifying these species based on their chemical composition. In this study, we employed, for the first time, a strategy combining gas chromatography-mass spectrometry (GC-MS) fingerprints and chemical patterns in order to identify HK and HI; it is also the first metabolomic study to date of HI as to chemical components. The obtained results revealed remarkable similarities in the chemical fingerprints, while significant differences were also observed. By employing hierarchical cluster analysis (HCA) and principal component analysis (PCA), based on the relative contents of their characteristic peaks, all 34 samples were successfully differentiated according to their species of origin, with samples from the same species forming distinct clusters. Moreover, nonadecanoic acid and behenic acid were exclusively detected in HK samples, further distinguishing them from HI samples. Additionally, the relative contents of lauric acid, tetradecanoic acid, pentadecanoic acid, n-hexadecanoic acid, palmitoleic acid, margaric acid, oleic acid, fenozan acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) exhibited significant differences between HK and HI (p < 0.0001), as determined by an unpaired t-test. Orthogonal partial least squares discriminant analysis (OPLS-DA) identified seven components (DHA, EPA, n-hexadecanoic acid, tetradecanoic acid, palmitoleic acid, octadecanoic acid, and margaric acid) with high discriminatory value (VIP value > 1). Thus, nonadecanoic acid, behenic acid, and these seven compounds can be utilized as chemical markers for distinguishing HK from HI. In conclusion, our study successfully developed a combined strategy of GC-MS fingerprinting and chemical pattern recognition for the identification of HK and HI, and we also discovered chemical markers that can directly differentiate between the two species. This study can provide a foundation for the authentication of Hippocampus and holds significant importance for the conservation of wild seahorse resources.

Piezoionic High Performance Hydrogel Generator and Active Protein Absorber via Microscopic Porosity and Phase Blending.

Generating electricity in hydrogel is very important but remains difficult. Hydrogel with electricity generation capability is more capable in bio-relevant tasks such as tissue engineering, artificial skin, or medical treatment, because electricity is indispensable in regulating physiological activities. Here, a porous and phase blending hydrogel structure for effective piezoionic electricity generation is developed. Dynamic electric field is generated taking advantage of the difference in streaming speeds of sodium and chloride in the material. Microscopic porosity and hydrophilic-hydrophobic phase blending are the two key factors for prominent piezoionic performance. Voltages as high as 600mV are first realized in hydrogels in response to medical ultrasound stimulation. The hydrogel structure is also subjective to effective substance exchange and can actively enrich proteins from surroundings under mechanical stimuli. Preliminary applications in neural stimulation, constructing complex spatial-temporal chemical and electric field distribution patterns, mimetic tactile sensor, sample pretreatment in fast detection, and enzyme immobilization are demonstrated.

Comparative Chemical Profiling and Antimicrobial/Anticancer Evaluation of Extracts from Farmed versus Wild Agelas oroides and Sarcotragus foetidus Sponges.

Marine sponges are highly efficient in removing organic pollutants and their cultivation, adjacent to fish farms, is increasingly considered as a strategy for improving seawater quality. Moreover, these invertebrates produce a plethora of bioactive metabolites, which could translate into an extra profit for the aquaculture sector. Here, we investigated the chemical profile and bioactivity of two Mediterranean species (i.e., Agelas oroides and Sarcotragus foetidus) and we assessed whether cultivated sponges differed substantially from their wild counterparts. Metabolomic analysis of crude sponge extracts revealed species-specific chemical patterns, with A. oroides and S. foetidus dominated by alkaloids and lipids, respectively. More importantly, farmed and wild explants of each species demonstrated similar chemical fingerprints, with the majority of the metabolites showing modest differences on a sponge mass-normalized basis. Furthermore, farmed sponge extracts presented similar or slightly lower antibacterial activity against methicillin-resistant Staphylococcus aureus, compared to the extracts resulting from wild sponges. Anticancer assays against human colorectal carcinoma cells (HCT-116) revealed marginally active extracts from both wild and farmed S. foetidus populations. Our study highlights that, besides mitigating organic pollution in fish aquaculture, sponge farming can serve as a valuable resource of biomolecules, with promising potential in pharmaceutical and biomedical applications.

Environmental inventory of mercury (Hg) for the marine shallow water hydrothermal system at Panarea, Italy

Hydrothermal fluids, hydrothermal gases, porewater and seawater were collected from the La Calcara (LC) hydrothermal area (n = 34). Additional samples were taken at Bottaro North (n = 2), Black Point (n = 3) and Panarea Harbor (n = 3). Total Hg (THg) porewater concentrations ranged from 300 to 6200 pM, while dissolved Hgdiss concentrations were generally lower by two to three orders of magnitude. Hydrothermal fluids had concentrations up to 26,000 pM. Mono- and dimethyl Hg (MeHg) were below detection. Total Hg in the gases (Hggas) ranged from 0.9 to 1899 nmol/m3.The THg concentration correlated positively with temperature (r = 0.86), while Hgdiss did not show any correlation (r = −0.02). The origin of Hg in the study area was interpreted to be hydrothermal. However, a clear trend was absent since ambient temperature porewaters had Hg concentrations as high as those porewaters with elevated temperatures. This was considered to be due to a combination of chemical reactions and complex flow patterns beneath the hydrothermal system. The concentration of Hg in the hydrothermal gases ranged from 0.9 to 1899 nmol/m3. This large range was ascribed to subsurface reactions with H2S and CH4 combined with the presence or absence of a sediment cover.Above the LC area, Hg concentrations were higher than those in Mediterranean seawater, indicating that the hydrothermal discharge adds Hg to the Panarea coastal ocean and its ecosystem. This effect is local regarding seawater chemistry and global Hg budgets since with distance Hg concentrations returned to values as expected for Mediterranean seawater. However, since most, if not all, marine food chains originate in coastal water, hydrothermal Hg may bioaccumulate in a given food chain. With >70 known marine shallow-water hydrothermal systems, this may be a worldwide phenomenon that warrants further study.

Diffusiophoresis-enhanced Turing patterns.

Turing patterns are fundamental in biophysics, emerging from short-range activation and long-range inhibition processes. However, their paradigm is based on diffusive transport processes that yield patterns with shallower gradients than those observed in nature. A complete physical description of this discrepancy remains unknown. We propose a solution to this phenomenon by investigating the role of diffusiophoresis, which is the propulsion of colloids by a chemical gradient, in Turing patterns. Diffusiophoresis enables robust patterning of colloidal particles with substantially finer length scales than the accompanying chemical Turing patterns. A scaling analysis and a comparison to recent experiments indicate that chromatophores, ubiquitous in biological pattern formation, are likely diffusiophoretic and the colloidal Péclet number controls the pattern enhancement. This discovery suggests that important features of biological pattern formation can be explained with a universal mechanism that is quantified straightforwardly from the fundamental physics of colloids.

New interactive functional indicator approach for river health assessment in an Asian temperate river: Comprehensive analysis of water chemistry, physical habitat, land use, and the biological disturbance of invasive alien species

Elucidating the responses of aquatic communities to environmental (e.g., chemical, habitat, and flow regime) and biological disturbances is essential to the maintenance and restoration of healthy ecosystems. This study investigated the interactions between environmental and biological disturbance factors and functional indicators of ecological health in 99 sampling sites along a temperate river. Variance tests and multivariate statistical tools, such as non-metric multidimensional scaling (NMDS) and generalized linear models (GLMs), were employed to evaluate the responses of functional indicator guilds and ecological river health to various in-stream chemical, physical, habitat, and land-use pattern factors along with the biological impact of invasive alien species (IAS). Variance testing revealed significant variation (χ2 > 6.2 and p < 0.05) in common species abundance and ecological functional guilds among spatial groups according to chemical pollution levels, land-use intensity, and land-use patterns. NMDS analysis and GLMs based on trophic, habitat, and tolerance guilds, and the results of the multi-metric index of biological integrity for fish, indicated statistically significant patterns in response to environmental disturbance, particularly chemical degradation associated with nutrient (nitrogen and phosphorus) enrichment and organic pollution, loss of gravel and cobble substrates, and intensified agricultural land use. The spatial pattern of IAS abundance was also significantly correlated with the alteration in fish community structures. This study underscores the often-unnoticed impact of high IAS abundance on river health, and its interactions with chemical and physical degradation resulting from agricultural and urban land uses. In summary, this study highlights the importance of addressing multiple environmental and biological disturbances to maintain and conserve the health of river systems.

Boundary-bound reactions: Pattern formation with and without hydrodynamics.

We study chemical pattern formation in a fluid between two flat plates and the effect of such patterns on the formation of convective cells. This patterning is made possible by assuming the plates are chemically reactive or release reagents into the fluid, both of which we model as chemical fluxes. We consider this as a specific example of boundary-bound reactions. In the absence of coupling with fluid flow, we show that the two-reagent system with nonlinear reactions admits chemical instabilities equivalent to diffusion-driven Turing instabilities. In the other extreme, when chemical fluxes at the two bounding plates are constant, diffusion-driven instabilities do not occur but hydrodynamic phenomena analogous to Rayleigh-Bénard convection are possible. Assuming we can influence the chemical fluxes along the domain and select suitable reaction systems, this presents a mechanism for the control of chemical and hydrodynamic instabilities and pattern formation. We study a generic class of models and find necessary conditions for a bifurcation to pattern formation. Afterwards, we present two examples derived from the Schnakenberg-Selkov reaction. Unlike the classical Rayleigh-Bénard instability, which requires a sufficiently large unstable density gradient, a chemohydrodynamic instability based on Turing-style pattern formation can emerge from a state that is uniform in density. We also find parameter combinations that result in the formation of convective cells whether gravity acts upwards or downwards relative to the reactive plate. The wave number of the cells and the direction of the flow at regions of high/low concentration depend on the orientation, hence, different patterns can be elicited by simply inverting the device. More generally, our results suggest methods for controlling pattern formation and convection by tuning reaction parameters. As a consequence, we can drive and alter fluid flow in a chamber without mechanical pumps by influencing the chemical instabilities.

Correction to “A Universal Approach to Fabricating 3D Chemical Patterns for Directed Self-Assembly of Block Copolymers with Density Multiplication”

Correction to “A Universal Approach to Fabricating 3D Chemical Patterns for Directed Self-Assembly of Block Copolymers with Density Multiplication”