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Magnetotelluric (MT) and audiomagnetotelluric (AMT) data are used to better understand the subsurface geology and mineral resources in the San Juan– Silverton caldera complex located near Silverton, Colorado, western United States, as part of the extensive southern Rocky Mountains volcanic field that covers much of southwestern Colorado and northern New Mexico. Seven MT and AMT profiles of varying lengths image resistivity structure to depths of ~5 km. The AMT inversion models characterize geophysical responses of near-surface lithologies, structures, and mineralized systems and also help corroborate airborne electromagnetic data at shallow levels. The MT inversion models extend our depth of investigation from near the surface to great depths (~5 km) and help to form hypotheses about roots of the hydrothermal plumbing that fed shallower mineralized systems. Subsurface high resistivities occur beneath intermediate-composition lava flows and Proterozoic units. Subsurface moderateto low-resistivity values may reflect hydrothermal plumbing that served as flow paths for mineralizing fluids and metallic ore formation. The model interpretations presented in this study could be utilized in remediation planning or mineral resource applications. The methods used could be applied to other watersheds with similar volcanic environments containing acid-generating historical mines or hydrothermally altered and mineralized source rocks. [ABSTRACT FROM AUTHOR]

The most abundant protein in the human body, collagen, is widely used in tissue culture and engineering applications, spanning from substrate functionalization to fibrillar architectures and three-dimensional constructs. Collagen piezoelectricity provides an opportunity to exploit electromechanical coupling in these applications, wherein an applied mechanical stress generates charge, which might influence ion screening, protein absorption, and cell response. In type I collagen, the polarization direction follows the fibril orientation. Thus, control of fibril orientation and size in a collagen film or membrane may provide control of the polarization, enabling the creation of regions of uniform polarization direction. Here, aligned substrate-supported type I collagen membranes having fibril sizes from ∼100–500 nm are deposited using different osmotic concentrations (90, 190, and 290 mOsm/kg, from low to high ionic strength) to investigate the correlation between fibril size and piezoelectric properties. Lateral piezoresponse force microscopy is used to show that regions of uniform polarization orientation, as determined through 2D correlation analysis, decrease with increasing fibril size. [ABSTRACT FROM AUTHOR]

Bound calcium ions stabilize many nonenveloped virions. Loss of Ca2+ from these particles appears to be a regulated part of entry or uncoating. The outer layer of an infectious rotavirus triple-layered particle (TLP) comprises a membrane-interacting protein (VP4) anchored by a Ca2+-stabilized protein (VP7). Membrane-coupled conformational changes in VP4 (cleaved to VP8* and VP5*) and dissociation of VP4 and VP7 accompany penetration of the double-layered inner capsid particle (DLP) into the cytosol. Removal of Ca2+ in vitro strips away both outer layer proteins; we and others have postulated that the loss of Ca2+ triggers molecular events in viral penetration. We have now investigated, with the aid of a fluorescent Ca2+ sensor, the timing of Ca2+ loss from entering virions with respect to the dissociation of VP4 and VP7. In live-cell imaging experiments, distinct fluorescent markers on the DLP and on VP7 report on outer layer dissociation and DLP release. The Ca2+ sensor, placed on VP5*, monitors the Ca2+ concentration within the membrane-bound vesicle enclosing the entering particle. Slow (1-min duration) loss of Ca2+ precedes the onset of VP7 dissociation by about 2 min and DLP release by about 7 min. Coupled with our previous results showing that VP7 loss follows tight binding to the cell surface by about 5 min, these data indicate that Ca2+ loss begins as soon as the particle has become fully engulfed within the uptake vesicle. We discuss the implications of these findings for the molecular mechanism of membrane disruption during viral entry. [ABSTRACT FROM AUTHOR]

The requirement of vitamins for core metabolic processes creates a unique set of pressures for arthropods subsisting on nutrient-limited diets. While endosymbiotic bacteria carried by arthropods have been widely implicated in vitamin provisioning, the underlying molecular mechanisms are not well understood. To address this issue, standardized predictive assessment of vitamin metabolism was performed in 50 endosymbionts of insects and arachnids. The results predicted that arthropod endosymbionts overall have little capacity for complete de novo biosynthesis of conventional or active vitamin forms. Partial biosynthesis pathways were commonly predicted, suggesting a substantial role in vitamin provisioning. Neither taxonomic relationships between host and symbiont, nor the mode of host-symbiont interaction were clear predictors of endosymbiont vitamin pathway capacity. Endosymbiont genome size and the synthetic capacity of nonsymbiont taxonomic relatives were more reliable predictors. We developed a new software application that also predicted that last-step conversion of intermediates into active vitamin forms may contribute further to vitamin biosynthesis by endosymbionts. Most instances of predicted vitamin conversion were paralleled by predictions of vitamin use. This is consistent with achievement of provisioning in some cases through upregulation of pathways that were retained for endosymbiont benefit. The predicted absence of other enzyme classes further suggests a baseline of vitamin requirement by the majority of endosymbionts, as well as some instances of putative mutualism. Adaptation of this workflow to analysis of other organisms and metabolic pathways will provide new routes for considering the molecular basis for symbiosis on a comprehensive scale. [ABSTRACT FROM AUTHOR]

This work highlights the possible use of vertically-aligned multiwall carbon nanotubes (VA-MWCNTs) as bottom electrodes for microelectronics, for example for memory applications. As a proof of concept BiFeO 3 (BFO) films were fabricated in-situ deposited on the surface of VA-MWCNTs by RF (radio frequency) magnetron sputtering. For in situ deposition temperature of 400 °C and deposition time up to 2 h, BFO films cover the MWCNTs and no damage occurs either in the film or MWCNTs. In spite of the macroscopic lossy polarization behaviour, the ferroelectric nature, domain structure and switching of these conformal BFO films was verified by piezo force microscopy. G type antiferromagnetic ordering with weak ferromagnetic ordering loop was proved for BFO films on VA-MWCNTs having a coercive field of 700 Oe. [ABSTRACT FROM AUTHOR]

Ferroelectric lithography, a recent method of fabricating functional interfaces, traditionally involves photoreduction on polarized ferroelectric surfaces at optical energies above the bandgap of the ferroelectric. In this work, for the first time, photochemical deposition of elemental Ag nanoparticles on a specifically poled lithium niobate substrate is reported, with a broad white‐light spectrum transmitted through the crystal. The transmitted light has energies only below the bandgap, leading to the conclusion that the Ag reduction proceeds through non‐linear effects, specifically, second harmonic generation. [ABSTRACT FROM AUTHOR]

Electrical bias-induced phase transitions underpin a wide range of applications from data storage to energy generation and conversion. The mechanisms behind these transitions are often quite complex and in many cases are extremely sensitive to local defects that act as centers for local transformations or pinning. Using ferroelectrics as an example, we review methods for probing bias-induced phase transitions and discuss the current limitations and challenges for extending the methods to field-induced phase transitions and electrochemical reactions in energy storage, biological and molecular systems. [Copyright &y& Elsevier]

It is important to know whether major mining districts in north-central Nevada are underlain by crust of the Archean Wyoming craton, known to contain major orogenic gold deposits or, alternatively, by accreted crust of the Paleoproterozoic Mojave province. Determining the location and orientation of the Archean-Proterozoic suture zone between these provinces is also important because it may influence subsequent patterns of sedimentation, deformation, magmatism, and hydrothermal activity. The suture zone is exposed in northeastern Utah and southwestern Wyoming and exhibits a southwest strike. In the Great Basin, the suture zone strike is poorly constrained because it is largely concealed below a Neoproterozoic-Paleozoic miogeocline and Cenozoic basin fill. Two-dimensional resistivity modeling of three regional north-south magnetotelluric sounding profiles in western Utah, north-central Nevada, and northeastern Nevada, and one east-west profile in northeastern Nevada, reveals a deeply penetrating (>10 km depth), broad (tens of kilometers) conductor (1-20 ohm-meters) that may be the Archean-Proterozoic suture zone, which formed during Early Proterozoic rifting of the continent and subsequent Proterozoic accretion. This major crustal conductor changes strike direction from southwest in Utah to northwest in eastern Nevada, where it broadens to ∼100 km width that correlates with early Paleozoic rifting of the continent. Our results suggest that the major gold belts may be over-isolated blocks of Archean crust, so Phanerozoic mineral deposits in this region may be produced, at least in part, from recycled Archean gold. Future mineral exploration to the east may yield large gold tonnages. [ABSTRACT FROM AUTHOR]

Macroscopic ferroelectric polarization switching, similar to other first-order phase transitions, is controlled by nucleation centres. Despite 50 years of extensive theoretical and experimental effort, the microstructural origins of the Landauer paradox, that is, the experimentally observed low values of coercive fields in ferroelectrics corresponding to implausibly large nucleation activation energies, are still a mystery. Here, we develop an approach to visualize the nucleation centres controlling polarization switching processes with nanometre resolution, determine their spatial and energy distribution and correlate them to local microstructure. The random-bond and random-field components of the disorder potential are extracted from positive and negative nucleation biases. Observation of enhanced nucleation activity at the 90∘ domain wall boundaries and intersections combined with phase-field modelling identifies them as a class of nucleation centres that control switching in structural-defect-free materials. [ABSTRACT FROM AUTHOR]

Functionality of biological and inorganic systems ranging from non-volatile computer memories and microelectromechanical systems to electromotor proteins and cellular membranes is ultimately based on the intricate coupling between electrical and mechanical phenomena. In the past decade, piezoresponse force microscopy (PFM) has been established as a powerful tool for nanoscale imaging, spectroscopy, and manipulation of ferroelectric and piczoelcctric materials. Here, we give an overview of the fundamental image formation mechanism in PFM and summarize recent theoretical and technological advances. In particular, we show that the signal formation in PFM is complementary to that in the scanning tunneling microscopy (STM) and atomic force microscopy (AFM) techniques, and we discuss the implications. We also consider the prospect of extending PFM beyond ferroelectric characterization for quantitative probing of electromechanical behavior in molecular and biological systems and high-resolution probing of static and dynamic polarization switching processes in low-dimensional ferroelectric materials and heterostructures. [ABSTRACT FROM AUTHOR]

The article presents a case study of a 45-year-old woman with plaques on the top of her hands for six months. The patient was diagnosed with chromoblastomycosis after a punch biopsy was performed on her arm. She was administered with oral terbinafine, itraconazole, and cryotherapy and then experienced improvement on her lesions after 12 months of therapy.

Peptide self-assemblies show intriguing and tunable physicochemical properties, and thus have been attracting increasing interest over the last two decades. However, the micro/nano-scale dimensions of the self-assemblies severely restrict their extensive applications. Inspired by nature, to genuinely realize the practical utilization of the bio-organic super-architectures, it is beneficial to further organize the peptide self-assemblies to integrate the properties of the individual supermolecules and fabricate higher-level organizations for smart functional devices. Therefore, cumulative studies have been reported on peptide microfabrication giving rise to diverse properties. This review summarizes the recent development of the microfabrication of peptide self-assemblies, discussing each methodology along with the diverse properties and practical applications of the engineered peptide large-scale, highly-ordered organizations. Finally, the current limitations of the state-of-the-art microfabrication strategies are critically assessed and alternative solutions are suggested. [ABSTRACT FROM AUTHOR]

The ferroelectric polarization switching behavior at the 24° (100) tilt grain boundary (GB) in an epitaxial multiferroic BiFeO3 bicrystal film is studied using piezoresponse force microscopy (PFM). The PFM amplitudes across positively and negatively poled GB regions suggest the presence of a frozen polarization component at the interface. The switching experiments demonstrate that the GB attracts the domain wall and acts as a pinning center. The PFM results are compared with conductive atomic force microscopy and spectroscopy, which suggest domain wall pinning at the GB can be partially attributed to increased conductance at the GB. [ABSTRACT FROM AUTHOR]

Time-resolved piezoresponse force spectroscopy (TR-PFS) and spectroscopic imaging are developed to probe the spatial variability of relaxation behavior in nanoscale ferroelectric materials and structures. TR-PFS was applied to study polarization dynamics in polyvinylidine fluoride and trifluoroethylene nanomesas. We demonstrate that polarization relaxation in ferroelectric polymers is slow even on the ∼10 nm length scale of piezoresponse force microscopy (PFM) signal generation. Furthermore, the relaxation times are found to be nonuniform within the nanomesa, indicative of a complex internal structure. The applicability of TR-PFM for studies of polarization dynamics in ferroelectric polymers and relaxors is discussed. [ABSTRACT FROM AUTHOR]

The image formation mechanism in piezoresponse force microscopy (PFM) of capacitor structures is analyzed. We demonstrate that the spatial resolution is a bilinear function of film and top electrode thicknesses and derive the corresponding analytical expressions. For many perovskites, the opposite contributions of d31 and d33 components can result in anomalous domain wall profiles. This analysis establishes the applicability limits of PFM for polarization dynamics studies in capacitors and applies them to other structural probes, including focused x-ray studies of capacitor structures. [ABSTRACT FROM AUTHOR]

Piezoresponse force microscopy has been used to manipulate and image polarization of ferroelectric polymer Langmuir-Blodgett films at the nanoscale, achieving polarization control with a resolution below 50 nm and imaging resolution below 5 nm. Individual regions showed square polarization-voltage hysteresis loops, demonstrating bistability of the polarization state. Arbitrary polarization patterns could be repeatedly written and erased with a resolution of 25 to 50 nm, limited by grain size, demonstrating the potential for high-density data storage and retrieval at densities exceeding 250 Gbits/in2. [ABSTRACT FROM AUTHOR]

An approach for high-frequency transport imaging, referred to as scanning frequency mixing microscopy (SFMM), is developed. Application of two high-frequency bias signals across an electroactive interface results in a low-frequency component due to interface nonlinearity. The frequency of a mixed signal is chosen within the bandwidth of the optical detector and can be tuned to the cantilever resonances. The SFMM signal is comprised of an intrinsic device contribution and a capacitive mixing contribution, and an approach to distinguish the two is suggested. This technique is illustrated on a model metal-semiconductor interface. The imaging mechanism and surface-tip contrast transfer are discussed. SFMM allows scanning probe microscopy based transport measurements to be extended to higher, ultimately gigahertz, frequency regimes, providing information on voltage derivatives of interface resistance and capacitance, from which device characteristics such as Schottky barrier height, etc., can be estimated. [ABSTRACT FROM AUTHOR]

Schizophrenia (SCZ) and Bipolar Disorder (BD) are heterogeneous psychiatric disorders with severe socioeconomic impacts and unknown pathogenesis, despite the plethora of genomics and genetic studies focused on protein-coding genes. However, the emerging consensus is that protein-coding genes are only the tip of the iceberg of the mammalian transcriptome, given the plethora of actively transcribed non-coding RNAs (ncRNAs). Circular RNAs (circRNAs) are a novel category of ncRNAs that are derived from the back-splicing and covalent joining of exons, yet lack the capacity to become translated into protein. Recent studies have suggested that circRNAs are enriched in the brain, are preferentially generated from brain plasticity-associated genes, and are abundant in dendrites and synapses. However, very little is known about the function of circRNAs in the human brain and their potential involvement in neuropsychiatric disease. Here we carried out systematic profiling of circRNA expression in a large cohort of human postmortem brains from subjects with SCZ and BD disorder and uncovered a subset of differentially expressed circRNAs produced from genes with known links to synaptic plasticity and neuronal excitability. We validated the expression of psychiatric disease-altered circRNAs in human postmortem brain with qRT-PCR and uncovered a subset of circRNAs that were also dysregulated in induced pluripotent stem cell-derived human neuronal progenitor and immature neuronal cultures from subjects with BD and SCZ. Analysis of RNA-Binding proteins (RBPs) that could bind to psychiatric disease-associated circRNAs revealed interactions with RBPs that affect alternative splicing and control of local translation in synapses. Ongoing experiments using circRNA shRNA knockdown in human stem cell-derived neuronal cultures are attempting to elucidate the function of SCZ- and BD-associated circRNAs in human neuronal development and maturation and their interplay with RBPs and disease-related molecular pathways. Collectively, our experiments will shed light into the unexplored role of circRNAs in brain function and disease. [ABSTRACT FROM AUTHOR]

How the two pathognomonic proteins of Alzheimer's disease (AD); amyloid ß (Aß) and tau, cause synaptic failure remains enigmatic. Certain synthetic and recombinant forms of these proteins are known to act concurrently to acutely inhibit long-term potentiation (LTP). Here, we examined the effect of early amyloidosis on the acute disruptive action of synaptotoxic tau prepared from recombinant protein and tau in patient-derived aqueous brain extracts. We also explored the persistence of the inhibition of LTP by different synaptotoxic tau preparations. A single intracerebral injection of aggregates of recombinant human tau that had been prepared by either sonication of fibrils (SτAs) or disulfide bond formation (oTau) rapidly and persistently inhibited LTP in rat hippocampus. The threshold for the acute inhibitory effect of oTau was lowered in amyloid precursor protein (APP)-transgenic rats. A single injection of synaptotoxic tau-containing AD or Pick's disease brain extracts also inhibited LTP, for over two weeks. Remarkably, the persistent disruption of synaptic plasticity by patient-derived brain tau was rapidly reversed by a single intracerebral injection of different anti-tau monoclonal antibodies, including one directed to a specific human tau amino acid sequence. We conclude that patient-derived LTP-disrupting tau species persist in the brain for weeks, maintaining their neuroactivity often in concert with Aß. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'. [ABSTRACT FROM AUTHOR]

We investigate a non-destructive approach for the characterization of proton exchanged layers in LiNbO3 with sub-micrometric resolution by means of piezoresponse force microscopy (PFM). Through systematic analyses, we identify a clear correlation between optical measurements on the extraordinary refractive index and PFM measurements on the piezoelectric d33 coefficient. Furthermore, we quantify the reduction of the latter induced by proton exchange as 83±2% and 68±3% of the LiNbO3 value, for undoped and 5mol. % MgO-doped substrates, respectively. [ABSTRACT FROM AUTHOR]

We have investigated the individual switching of nanoscale capacitors by piezoresponse force microscopy. Nanoscale epitaxial ferroelectric capacitors with terabyte per inch square equivalent density were fabricated by the deposition of top electrodes onto a pulsed laser deposited lead zirconate titanate thin film by electron beam evaporation through ultrathin anodic aluminum oxide membrane stencil masks. Using bias pulses, the nanoscale capacitors were uniformly switched and proved to be individually addressable. These film-based nanoscale capacitors might be a feasible alternative for high-density mass storage memory applications with near terabyte per inch square density due to the absence of any cross-talk effects. [ABSTRACT FROM AUTHOR]

[Display omitted] A library of composite polymer networks (CPNs) were formed by combining Pluronic F127, as the primary gelator, with a range of di-acrylate functionalised PEG polymers, which tune the rheological properties and provide UV crosslinkability. A coarse-grained sol–gel room temperature phase diagram was constructed for the CPN library, which identifies PEG-dependent disruption of micelles as leading to liquefication. Small angle X-ray scattering and rheological measurements provide detailed insight into; (i) micelle-micelle ordering; (ii) micelle-micelle disruption, and; (iii) acrylate-micelle disruption; with contributions that depend on composition, including weak PEG chain length and end group effects. The influence of composition on 3D extrusion printability through modulation of the cohesive/hydrophobic interactions was assessed. It was found that only micelle content provides consistent changes in printing fidelity, controlled largely by printing conditions (pressure and feed rate). Finally, the hydrogels were shown to be UV photo-crosslinkable, which further improves fidelity and structural integrity, and usefully reduces the mesh size. Our results provide a guide for design of 3D-printable CPN inks for future biomedical applications. [ABSTRACT FROM AUTHOR]

Photocatalysts for oxidation reactions are crucial for a wide variety of industrial activities. Here, we describe a framework consisting of silver nanomaterials atop Mg-doped lithium niobate. This substrate under white light irradiation is demonstrated to support the oxidation of compounds, such as p-aminothiophenol, through the activation of charge transfer processes. This study highlights the use of doped lithium niobate materials as semiconductor platforms for plasmonic photocatalysis. [ABSTRACT FROM AUTHOR]

Piezoelectric diphenylalanine peptide nanotubes (PNTs) have recently been demonstrated in energy harvesting applications, typically based on vertically aligned PNTs that generate charge when pressed. In this work, we use a wettability difference and an applied electric field to align PNTs and PNT-based composites on flexible substrates. Open-circuit voltages and short-circuit currents exceeding 6 V and 60 nA, respectively, are achieved by bending the substrate, opening up the use of horizontally aligned PNTs as flexible energy harvesting substrates. [ABSTRACT FROM AUTHOR]

The functional role of collagen piezoelectricity has been under debate since the discovery of piezoelectricity in bone in 1957. The possibility that piezoelectricity plays a role in bone remodeling has generated interest in the investigation of this effect in relevant physiological conditions; however, there are conflicting reports as to whether collagen is piezoelectric in a humid environment. In macroscale measurements, the piezoelectricity in hydrated tendon has been shown to be insignificant compared to dehydrated tendon, whereas, at the nanoscale, the piezoelectric effect has been observed in both dry and wet bone using piezoresponse force microscopy (PFM). In this work, the electromechanical properties of type I collagen from a rat tail tendon have been investigated at the nanoscale as a function of humidity using lateral PFM (LPFM) for the first time. The relative humidity (RH) was varied from 10% to 70%, allowing the piezoelectric behavior to be studied dry, humid, as well as in the hydrated range for collagen in physiological bone (12% moisture content, corresponding to 40–50% RH). The results show that collagen piezoresponse can be measured across the humidity range studied, suggesting that piezoelectricity remains a property of collagen at a biologically relevant humidity. [ABSTRACT FROM AUTHOR]

Germanium nanowire (GeNW) electrodes have shown great promise as high-power, fast-charging alternatives to silicon-based electrodes, owing to their vastly improved Li ion diffusion, electron mobility and ionic conductivity. Formation of the solid electrolyte interphase (SEI) on the anode surface is critical to electrode performance and stability but is not completely understood for NW anodes. Here, a systematic study characterizing pristine and cycled GeNWs in charged and discharged states with SEI layer present and removed is performed using Kelvin probe force microscopy in air. Correlating changes in the morphology of the GeNW anodes with contact potential difference mapping at different cycles provides insight into SEI layer formation and growth, and the effect of the SEI on battery performance. [ABSTRACT FROM AUTHOR]

Self‐assembling nanostructured peptide gels are promising materials for sensing, drug delivery, and energy harvesting. Of particular interest are short diphenylalanine (FF) peptides modified with 9‐fluorenylmethyloxycarbonyl (Fmoc), which promotes the association of the peptide building blocks. Fmoc‐FF gels generally form fibrous networks and while other structures have been demonstrated, further control of the gelation and resulting ordered three‐dimensional structures potentially offers new possibilities in tissue engineering, sensing, and drug release applications. Herein, we report that the structure tunability of Fmoc‐FF gels can be achieved by controlling the water content and the temperature. We further explore the incorporation of metal nanoparticles in the formation of the gel to enable optical sensing applications based on hybrid Fmoc‐FF‐nanoparticle microspheres. Finally, fluorescence lifetime imaging microscopy reveals a correlation between lifetime and reduced bandgap, in support of a semiconductor‐induced charge transfer mechanism that might also increase the stability of an excited state of a probe molecule. The observations potentially further widen the use of these peptide materials in bioimaging and sensing applications. [ABSTRACT FROM AUTHOR]

Self-assembly offers potential routes for large-scale, rapid, and cost-effective surface-enhanced Raman scattering (SERS) substrate designs. Here, a highly sensitive SERS template is reported, which utilizes aligned diphenylalanine nanotubes to form a dense packing arrangement of plasmon-active silver nanoparticles. The template is stable under high laser illumination with a power density of ~6.25 MW/cm2 in comparison to only silver nanoparticles and enables picomolar and femtomolar probe molecule concentrations to be probed, indicative of single-molecule SERS detection. [ABSTRACT FROM AUTHOR]

Atomic force microscopy (AFM) has been utilized for nanomechanical machining of various materials including polymers, metals, and semiconductors. Despite being important candidate materials for a wide range of applications including data storage and actuators, ferroelectric materials have rarely been machined via AFM. AFM-based machining of ferroelectric nanostructures offers advantages over established techniques, such as bottom-up approaches and focused ion beam milling, in select cases where low damage and low-cost modification of already-fabricated thin films are required. Through a systematic investigation of a broad range of AFM parameters, we demonstrate that AFM-based machining provides a low-cost option to rapidly modify local regions of the film, as well as fabricate a range of different nanostructures, including a nanocapacitor array with individually addressable ferroelectric elements. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) metal borides are a class of ceramic materials with diverse structural and topological properties. These diverse material properties of metal borides are what forms the basis of their interdisciplinarity and their applicability in various research fields. In this study, we highlight which fundamental and practical parameters need to be taken into consideration when designing nanomaterials for specific applications. A simple one-pot chemical reduction method was applied for the synthesis of manganese mono-boride nanoflakes at room temperature. How the specific surface area and boron-content of the as-synthesized manganese mono-boride nanoflakes influence their magnetic and electrocatalytic properties is reported. The sample with the highest specific surface area and boron content demonstrated the best magnetic and electrocatalytic properties in the HER. Whereas the sample with the lowest specific surface area and boron content exhibited the best electric conductivity and electrocatalytic properties in the OER. [ABSTRACT FROM AUTHOR]

The bactericidal properties of chemically patterned lithium niobate substrates under a super-bandgap UV light source is established. UV irradiation of lithium niobate surfaces inoculated with bacteria leads to antimicrobial activity compared to a glass substrate under similar conditions, as determined by surface enhanced Raman spectroscopy and corroborated with a fluorescence-based live/dead assay. This finding may expand the possible biomedical applications of lithium niobate. [ABSTRACT FROM AUTHOR]

Recent molecular modeling methods using Markovian descriptions of conformational states of biomolecular systems have led to powerful analysis frameworks that can accurately describe their complex dynamical behavior. In conjunction with enhanced sampling methods, such as replica exchange molecular dynamics (REMD), these frameworks allow the systematic and accurate extraction of transition probabilities between the corresponding states, in the case of Markov state models, and of statistically-optimized transition rates, in the case of the corresponding coarse master equations. However, applying automatically such methods to large molecular dynamics (MD) simulations, with explicit water molecules, remains limited both by the initial ability to identify good candidates for the underlying Markovian states and by the necessity to do so using good collective variables as reaction coordinates that allow the correct counting of inter-state transitions at various lag times. Here, we show that, in cases when representative molecular conformations can be identified for the corresponding Markovian states, and thus their corresponding collective evolution of atomic positions can be calculated along MD trajectories, one can use them to build a new type of simple collective variable, which can be particularly useful in both the correct state assignment and in the subsequent accurate counting of inter-state transition probabilities. In the case of the ubiquitously used root-mean-square deviation (RMSD) of atomic positions, we introduce the relative RMSD (RelRMSD) measure as a good reaction coordinate candidate. We apply this method to the analysis of REMD trajectories of amyloid-forming diphenylalanine (FF) peptides—a system with important nanotechnology and biomedical applications due to its self-assembling and piezoelectric properties—illustrating the use of RelRMSD in extracting its temperature-dependent intrinsic kinetics, without a priori assumptions on the functional form (e.g., Arrhenius or not) of the underlying conformational transition rates. The RelRMSD analysis enables as well a more objective assessment of the convergence of the REMD simulations. This type of collective variable may be generalized to other observables that could accurately capture conformational differences between the underlying Markov states (e.g., distance RMSD, the fraction of native contacts, etc.). [ABSTRACT FROM AUTHOR]

There are limited studies on predisposing factors for COVID-19 positivity in asymptomatic pregnant women. The literature published to date on asymptomatic COVID-19 pregnant carriers does not focus on pregnancy or pre-pregnancy comorbidities. We wanted to identify risk factors for COVID-19 in asymptomatic pregnant women. We performed a retrospective chart review of 263 asymptomatic pregnant women admitted to labour and delivery at New York City Health + Hospitals/Lincoln. We analysed the association between race, body mass index (BMI), smoking, indication for admission, gravidity, parity, pre-pregnancy comorbidity, pregnancy comorbidity via uni- and multivariate statistical tests. Only Hispanic race was significant in the univariate analysis (p =.049). At the post-hoc analysis, Hispanics had a higher proportion of COVID-19 cases compared to non-Hispanic Blacks (p =.019). No variables were significantly associated with COVID-19 positivity in the multivariate analysis. Hispanic race appears to be a risk factor for asymptomatic COVID-19 infection during pregnancy. We speculate that the cultural and socioeconomic reality of Hispanic women living in our community leads to more exposure opportunities and therefore, a higher infection rate. What is already known on this subject? Little is known on the role of comorbidities and risk factors that can favour COVID-19 infection during pregnancy. What do the results of this study add? We found that Hispanic pregnant asymptomatic women had a higher rate of COVID-19 in comparison to non-Hispanic Black women. Pre-pregnancy comorbidities such as pregestational diabetes, hypertension and asthma were not associated with COVID-19 positivity. What are the implications of these findings for clinical practice and/or further research? The reasons why the Hispanic race is more affected by COVID-19 during pregnancy is unclear. The social environment of Hispanic women living in our community, such as their tendency to live in multigenerational and multi-family households, might contribute to a higher infection rate. More resources might be dedicated in the future to Hispanic-dense neighbourhoods. [ABSTRACT FROM AUTHOR]

Nature has inspired the design of complex hierarchical structures in the field of material science. Diatoms, unicellular algae with a hallmark intricate siliceous cell wall, have provided such a stimulus. Altering the chemistry of the diatom frustule has been explored to expand on the potential application of diatoms. The ability to modify the diatom in vivo opens the possibility to tailor the diatom to the end application. Herein, we report the chemical modification of the living diatom T. weissflogii using a titania precursor, titanium (IV) bis-(ammonium lactato)-dihydroxide (TiBALDH). Incorporation of Ti into the diatom is achieved via repeated treatment of cultures with non-toxic concentrations of TiBALDH. The characteristic architectural features of the diatom are unaltered following chemical modification. Transformation of the living diatom provides opportunity to confer novel structural, chemical or functional properties upon the diatom. We report on a photocatalytic ability imparted upon the TiBALDH-modified diatom. [ABSTRACT FROM AUTHOR]

[Display omitted] Hydrogels loaded with magnetic iron oxide nanoparticles that can be patterned and which controllably induce hyperthermic responses on AC-field stimulation are of interest as functional components of next-generation biomaterials. Formation of nanocomposite hydrogels is known to eliminate any Brownian contribution to hyperthermic response (reducing stimulated heating) while the Néel contribution can also be suppressed by inter-particle dipolar interactions arising from aggregation induced before or during gelation. We describe the ability of graphene oxide (GO) flakes to restore the hyperthermic efficiency of soft printable hydrogels formed using Pluronics F127 and PEGylated magnetic nanoflowers. Here, by varying the amount of GO in mixed nanocomposite suspensions and gels, we demonstrate GO-content dependent recovery of hyperthemic response in gels. This is due to progressively reduced inter-nanoflower interactions mediated by GO, which largely restore the dispersed-state Néel contribution to heating. We suggest that preferential association of GO with the hydrophobic F127 blocks increases the preponderance of cohesive interactions between the hydrophilic blocks and the PEGylated nanoflowers, promoting dispersion of the latter. Finally we demonstrate extrusion-based 3D printing with excellent print fidelity of the magnetically-responsive nanocomposites, for which the inclusion of GO provides significant improvement in the spatially-localized open-coil heating response, rendering the prints viable components for future cell stimulation and delivery applications. [ABSTRACT FROM AUTHOR]

Conductivity in Mg doped lithium niobate (Mg:LN) plays a key role in the reduction of photorefraction and is therefore widely exploited in optical devices. However, charge transport through Mg:LN and across interfaces such as electrodes also yields potential electronic applications in devices with switchable conductivity states. Furthermore, the introduction of proton exchanged (PE) phases in Mg:LN enhances ionic conductivity, thus providing tailorability of conduction mechanisms and functionality dependent on sample composition. To facilitate the construction and design of such multifunctional electronic devices based on periodically PE Mg:LN or similar ferroelectric semiconductors, fundamental understanding of charge transport in these materials, as well as the impact of internal and external interfaces, is essential. In order to gain insight into polarization and interface dependent conductivity due to band bending, UV illumination, and chemical reactivity, wedge shaped samples consisting of polar oriented Mg:LN and PE phases were investigated using conductive atomic force microscopy. In Mg:LN, three conductivity states (on/off/transient) were observed under UV illumination, controllable by the polarity of the sample and the externally applied electric field. Measurements of currents originating from electrochemical reactions at the metal electrode-PE phase interfaces demonstrate a memresistive and rectifying capability of the PE phase. Furthermore, internal interfaces such as domain walls and Mg:LN-PE phase boundaries were found to play a major role in the accumulation of charge carriers due to polarization gradients, which can lead to increased currents. The insight gained from these findings yield the potential for multifunctional applications such as switchable UV sensitive micro- and nanoelectronic devices and bistable memristors. [ABSTRACT FROM AUTHOR]

The preferential deposition of metal nanoparticles onto periodically poled lithium niobate surfaces, whereby photogenerated electrons accumulate in accordance with local electric fields and reduce metal ions from solution, is known to depend on the intensity and wavelength of the illumination and the concentration of the solution used. Here, it is shown that for identical deposition conditions (wavelength, intensity, concentration), post-poling annealing for 10 h at 200 °C modifies the surface reactivity through the reorientation of internal defect fields. Whereas silver nanoparticles deposit preferentially on the +z domains on unannealed crystals, the deposition occurs preferentially along 180° domain walls for annealed crystals. In neither case is the deposition selective; limited deposition occurs also on the unannealed -z domain surface and on both annealed domain surfaces. The observed behavior is attributed to a relaxation of the poling-induced defect frustration mediated by Li+ ion mobility during annealing, which affects the accumulation of electrons, thereby changing the surface reactivity. The evolution of the defect field with temperature is corroborated using Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Scanning Probe Microscopy (SPM) based techniques probe material properties over microscale regions with nanoscale resolution, ultimately resulting in investigation of mesoscale functionalities. Among SPM techniques, piezoresponse force microscopy (PFM) is a highly effective tool in exploring polarization switching in ferroelectric materials. However, its signal is also sensitive to sample‐dependent electrostatic and chemo‐electromechanical changes. Literature reports have often concentrated on the evaluation of the Off‐field piezoresponse, compared to On‐field piezoresponse, based on the latter's increased sensitivity to non‐ferroelectric contributions. Using machine learning approaches incorporating both Off‐ and On‐field piezoresponse response as well as Off‐field resonance frequency to maximize information, switching piezoresponse in a defect‐rich Pb(Zr,Ti)O3 thin film is investigated. As expected, one major contributor to the piezoresponse is mostly ferroelectric, coupled with electrostatic phenomena during On‐field measurements. A second component is electrostatic in nature, while a third component is likely due to a superposition of multiple non‐ferroelectric processes. The proposed approach will enable deeper understanding of switching phenomena in weakly ferroelectric samples and materials with large chemo‐electromechanical response. [ABSTRACT FROM AUTHOR]

Mg doped lithium niobate (Mg:LN) exhibits several advantages over undoped LN such as resistance to photorefraction, lower coercive fields, and p-type conductivity that is particularly pronounced at domain walls and opens up a range of applications, e.g., in domain wall electronics. Engineering of precise domain patterns necessitates well founded knowledge of switching kinetics, which can differ significantly from that of undoped LN. In this work, the role of humidity and sample composition in polarization reversal has been investigated under application of the same voltage waveform. Control over domain sizes has been achieved by varying the sample thickness and initial polarization as well as atmospheric conditions. In addition, local introduction of proton exchanged phases allows for inhibition of domain nucleation or destabilization, which can be utilized to modify domain patterns. Polarization dependent current flow, attributed to charged domain walls and band bending, demonstrates the rectifying ability of Mg:LN in combination with suitable metal electrodes that allow for further tailoring of conductivity. [ABSTRACT FROM AUTHOR]

Controlling ferroelectric switching in Mg doped lithium niobate (Mg:LN) is of fundamental importance for optical device and domain wall electronics applications that require precise domain patterns. Stable ferroelectric switching has been previously observed in undoped LN layers above proton exchanged (PE) phases that exhibit reduced polarization, whereas PE layers have been found to inhibit lateral domain growth. Here, Mg doping, which is known to significantly alter ferroelectric switching properties including coercive field and switching currents, is shown to inhibit domain nucleation and stability in Mg:LN above buried PE phases that allow for precise ferroelectric patterning via domain growth control. Furthermore, piezoresponse force microscopy (PFM) and switching spectroscopy PFM reveal that the voltage at which polarization switches from the "up" to the "down" state increases with increasing thickness in pure Mg:LN, whereas the voltage required for stable back switching to the original "up" state does not exhibit this thickness dependence. This behavior is consistent with the presence of an internal frozen defect field. The inhibition of domain nucleation above PE interfaces, observed in this study, is a phenomenon that occurs in Mg:LN but not in undoped samples and is mainly ascribed to a remaining frozen polarization in the PE phase that opposes polarization reversal. This reduced frozen depolarization field in the PE phase also influences the depolarization field of the Mg:LN layer above due to the presence of uncompensated polarization charge at the PE-Mg:LN boundary. These alterations in internal electric fields within the sample cause long-range lattice distortions in Mg:LN via electromechanical coupling, which were corroborated with complimentary Raman measurements. [ABSTRACT FROM AUTHOR]

Thymine (2-oxy-4-oxy-5 methyl pyrimidine) is one of the four nucleobases of deoxyribonucleic acid (DNA). In the DNA molecule, thymine binds to adenine via two hydrogen bonds, thus stabilizing the nucleic acid structure and is involved in pairing and replication. Here, we show that synthetic thymine microcrystals grown from the solution exhibit local piezoelectricity and apparent ferroelectricity, as evidenced by nanoscale electromechanical measurements via Piezoresponse Force Microscopy. Our experimental results demonstrate significant electromechanical activity and polarization switchability of thymine, thus opening a pathway for piezoelectric and ferroelectricbased applications of thymine and, perhaps, of other DNA nucleobase materials. The results are supported by molecular modeling of polarization switching under an external electric field. [ABSTRACT FROM AUTHOR]

High aspect ratio (HAR) nanoneedle arrays can be used to tune the intrinsic properties of substrates such as their wettability and reflectivity. Here, a simple and scalable fabrication method for producing dense arrays of freestanding polyethylene glycol (PEG) nanoneedles with sub 50 nm tips and surface coverage up to 83 needles per µm2 is presented. Two distinct sets of silicon nanoneedle master arrays with base diameters between 15 and 265 nm and heights between 146 and 613 nm are fabricated using block copolymer micelle lithography. Replication of selected silicon masters using photocurable polymers produces HAR PEG nanoneedle arrays with feature base diameters ranging between 15 and 292 nm and heights between 133 and 656 nm. At their maximum, the aspect ratio of the pillars is 4.6. PEG nanoneedle arrays are produced using polymers with two different molecular weights as well as two different photoinitiators, showing the versatility of the process. [ABSTRACT FROM AUTHOR]

This work reports on direct crystallization of PbZr 0.53 Ti 0.47 O 3 (PZT) thin films on glass and polymeric substrates, using pulsed thermal processing (PTP). Specifically, xenon flash lamps deliver pulses of high intensity, short duration, broadband light to the surface of a chemical solution deposited thin film, resulting in the crystallization of the film. Structural analysis by X-ray diffraction (XRD) and transmission electron microscopy show the existence of perovskite structure in nano-sized grains (≤5 nm). Local functional analysis by band excitation piezoelectric spectroscopy and electrostatic force microscopy confirm the presence of a ferroelectric phase and retention of voltage-written polarization for multiple days. Based on structural and functional analyses, strategies are discussed for optimization of pulse voltage and duration for the realization of crystalline ferroelectric thin films. For ∼200 nm-thick PZT films on glass substrates, 500 μs-long pulses were required for crystallization, starting with 100 pulses at 350 V, 10 or 25 pulses at 400 V and in general lower number of pulses at higher voltages (resulting in higher radiant energy). Overall power densities of >6.4 kW/cm2 were needed for appearance of peaks corresponding to the perovskite phase in the XRD. Films on glass processed at 350–400 V had a higher degree of 111-oriented perovskite grains. Higher applied radiant energy (through increased pulse voltage or count) resulted in more random and/or partially 001-oriented films. For ∼1 μm-thick PZT films on polymeric substrates, 10 to 25 250 μs-long pulses at voltages ranging between 200 to 250 V, corresponding to power densities of ∼2.8 kW/cm2, were optimal for maximized perovskite phase crystallization, while avoiding substrate damage. [ABSTRACT FROM AUTHOR]

Therapeutic factors secreted by mesenchymal stem cells (MSCs) promote angiogenesis in vivo. However, delivery of MSCs in the absence of a cytoprotective environment offers limited efficacy due to low cell retention, poor graft survival, and the nonmaintenance of a physiologically relevant dose of growth factors at the injury site. The delivery of stem cells on an extracellular matrix (ECM)-based platform alters cell behavior, including migration, proliferation, and paracrine activity, which are essential for angiogenesis. We demonstrate the biophysical and biochemical effects of preconditioning human MSCs (hMSCs) for 96 h on a three-dimensional (3D) ECM-based microgel platform. By altering the macromolecular concentration surrounding cells in the microgels, the proangiogenic phenotype of hMSCs can be tuned in a controlled manner through cell-driven changes in extracellular stiffness and “outside-in” integrin signaling. The softest microgels were tested at a low cell dose (5 × 104 cells) in a preclinical hindlimb ischemia model showing accelerated formation of new blood vessels with a reduced inflammatory response impeding progression of tissue damage. Molecular analysis revealed that several key mediators of angiogenesis were up-regulated in the low-cell-dose microgel group, providing a mechanistic insight of pathways modulated in vivo. Our research adds to current knowledge in cell-encapsulation strategies by highlighting the importance of preconditioning or priming the capacity of biomaterials through cell–material interactions. Obtaining therapeutic efficacy at a low cell dose in the microgel platform is a promising clinical route that would aid faster tissue repair and reperfusion in “no-option” patients suffering from peripheral arterial diseases, such as critical limb ischemia (CLI). [ABSTRACT FROM AUTHOR]

One of the key limiting factors in the quantitative interpretation of piezoresponse force microscopy (PFM) is the lack of knowledge on the effective tip geometry. Here the authors derive analytical expressions for a 180° domain wall profile in PFM for the point charge, sphere plane, and disk electrode models of the tip. An approach for the determination of the effective tip parameters from the wall profile is suggested and illustrated for several ferroelectric materials. The calculated tip parameters can be used self-consistently for the interpretation of PFM resolution and spectroscopy data, i.e., linear imaging processes. [ABSTRACT FROM AUTHOR]

Piezoresponse force spectroscopy (PFS) has emerged as a powerful technique for probing highly localized polarization switching in ferroelectric materials. The application of a dc bias to a scanning probe microscope tip in contact with a ferroelectric surface results in the nucleation and growth of a ferroelectric domain below the tip, detected though the change of local electromechanical response. Here, we analyze the signal formation mechanism in PFS by deriving the main parameters of domain nucleation in a semi-infinite ferroelectric semiconductor material. The effect of surface screening and finite Debye length on the switching behavior is established. We predict that critical domain sizes and activation barrier in piezoresponse force microscopy (PFM) is controlled by the screening mechanisms. The relationships between domain parameters and PFM signal is established using a linear Green’s function theory. This analysis allows PFS to be extended to address phenomena such as domain nucleation in the vicinity of defects and local switching centers in ferroelectrics. [ABSTRACT FROM AUTHOR]

Further to conventional linear, branched, crosslinked, and dendritic polymers, single chain cyclized/knotted polymers (SCKPs) have emerged as a new class of polymer structure with unique properties. Herein, the development of bacteria‐resistant SCKPs is reported and the effect of this structure on the resistance of polymer materials to bacteria is investigated. Four SCKPs were synthesized by reversible addition fragmentation chain transfer (RAFT) homopolymerization of multivinyl monomers (MVMs) and then crosslinked by UV light to form SCKP films. Regardless of MVM type used, the resulting SCKP films showed much higher resistance to bacteria, and up to 75 % less bacterial attachment and biofilm formation, in comparison with the corresponding non‐SCKP films. This is due to the altered surface morphology and hydrophobicity of the SCKP films. These results highlight the critical role of the SCKP structure in enhancing the resistance of polymeric materials to bacteria. [ABSTRACT FROM AUTHOR]

Further to conventional linear, branched, crosslinked, and dendritic polymers, single chain cyclized/knotted polymers (SCKPs) have emerged as a new class of polymer structure with unique properties. Herein, the development of bacteria‐resistant SCKPs is reported and the effect of this structure on the resistance of polymer materials to bacteria is investigated. Four SCKPs were synthesized by reversible addition fragmentation chain transfer (RAFT) homopolymerization of multivinyl monomers (MVMs) and then crosslinked by UV light to form SCKP films. Regardless of MVM type used, the resulting SCKP films showed much higher resistance to bacteria, and up to 75 % less bacterial attachment and biofilm formation, in comparison with the corresponding non‐SCKP films. This is due to the altered surface morphology and hydrophobicity of the SCKP films. These results highlight the critical role of the SCKP structure in enhancing the resistance of polymeric materials to bacteria. [ABSTRACT FROM AUTHOR]

Abstract Electrically conductive materials have been highlighted in the biomedical and food packaging areas. Conventional electrically conductive polymers have limited biodegradability and biocompatibility and should be replaced by suitable biomaterials. Herein, electrically conductive bionanocomposites of chitosan and reduced graphene oxide were produced by a green methodology. The reduced graphene oxide was hydrothermally reduced in the presence of caffeic acid and was dispersed into chitosan. The final bionanocomposites achieved an electrical conductivity of 0.7 S/m in-plane and 2.1 × 10−5 S/m through-plane. The reduced graphene oxide promoted a great enhancement of antioxidant activity and a mechanical reinforcement of chitosan matrix, increasing the tensile strength and decreasing the water solubility. The electrical conductivity, mechanical properties and antioxidant activity of the bionanocomposites can be tuned according to the filler content. These active bionanocomposites, prepared using a green methodology, revealed good electrical and mechanical properties, which make them promising materials for food packaging and biological applications. [ABSTRACT FROM AUTHOR]