Small Scale Research Articles

Mykonos: A pulsed power driver for science and innovation

Sandia National Laboratories has been operating the Mykonos linear transformer driver (LTD) in a five-cavity configuration since 2014. The machine operates at 1MA output current, 500kV output voltage, with a 10–90% current rise time of 85ns, which enables small scale physics and engineering pulsed power experiments. Mykonos provides hands-on pulsed power experimental training for students and staff alongside senior Sandia scientists in an environment that is more accessible than the Z Facility. Over the years, we have fielded and accumulated a wide variety of optical, x-ray and electrical diagnostics and we are preparing to open this facility to outside users. Here, we are presenting the pulsed power and diagnostic capability of Mykonos as well as some recent experiments that have been performed on the facility. The goal of this publication is to attract researchers across the pulsed power and high energy density (HED) community to collaborate with Sandia on exciting, innovative science and to train the next generation of researchers for the National Nuclear Security Agency (NNSA) and the nation. As such, we have established a Mykonos Academic Access Program (MAAP) as part of ZNetUS to enable academic utilization of the Mykonos Pulsed Power Facility.

Damping efficiency of the fractional Duffing system and an assessment of its solution accuracy

Dynamical systems with high damping efficiency in a wide frequency band can be useful on a small scale – for harvesting energy from ambient vibrations, and on a large scale – for damping harmful vibrations of mechanical structures. In this paper we present an assessment of the quality of solutions and damping efficiency of systems with fractional order derivatives. To simulate the fractional system the fourth-order Runge–Kutta method and Grünwald–Letnikov methods are used. We propose a coefficient for assessing the quality of solutions to fractional systems by reference to the quality of the calculated energy balance. As an exemplary system we study the Duffing model with embedded additional fractional-order derivative terms. Based on this coefficient, intervals of key numerical simulation parameters are determined to ensure the appropriate quality for the calculations of energy flows and energy balance. The determined values of these parameters are then used in tests of the damping efficiency of the studied system. Our results show that by modifying the fractional terms it is possible to configure a system that exhibits a “broadband effect”, i.e. a system that is characterized by high-amplitude vibrations and, consequently, high energy efficiency in a wide range of excitation frequencies.

Factors controlling peat soil thickness and carbon storage in temperate peatlands based on UAV high-resolution remote sensing

Peatlands store a large amount of carbon. However, peatlands are complex ecosystems, and acquiring reliable estimates of how much carbon is stored underneath the Earth’s surface is inherently challenging, even at small scales. Here, we aim to establish links between the above- and below-ground factors that control soil carbon status, identify the key environmental variables associated with carbon storage, as well as to explore the potential for using Unmanned Aerial Vehicle (UAV) remote sensing for spatial mapping of peatlands. We combine UAVs equipped with Red-Green-Blue (RGB), multispectral, thermal infrared, and light detection and ranging (LiDAR) sensors with ground-penetrating radar (GPR) technology and traditional field surveys to provide a comprehensive, 3-dimensional mapping of a peatland hillslope-floodplain landscape in the Belgian Hautes Fagnes. Our results indicate that both peat thickness and soil organic carbon (SOC) stock (top 1 m) are spatially heterogeneous and that the contributions from the surface topography to peat thickness and SOC stock varied from micro- to macro-scales. Peat thickness was more strongly controlled by macro-topography (R2 = 0.46) than SOC stock, which was more influenced by micro-topography (R2 = 0.21). Current vegetation had little predictive power for explaining their spatial variability. Additionally, the UAV data provided accurate estimates of both peat thickness and SOC stock, with RMSE and R2 values of 0.16 m and 0.85 for the peat thickness, and 59.25 t/ha and 0.85 for the SOC stock. However, similar performance can already be achieved by using only topographical data from the LiDAR sensor (for peat thickness) and a combination of peat thickness and topography (for SOC stock) as predictor variables. Our study bridges the gap between surface observations and the hidden carbon reservoir below. This not only allows us to improve our ability to assess the spatial distribution of SOC stocks, but also contributes to our understanding of the environmental factors associated with SOC storage in these highly heterogeneous landscapes, providing insights for environmental science and climate projections.

Synthesizing Lipid Nanoparticles by Turbulent Flow in Confined Impinging Jet Mixers.

Lipid nanoparticles (LNPs) have demonstrated their enormous potential as therapeutic delivery vehicles, as evidenced by the approval and global usage of two COVID-19 messenger RNA (mRNA) vaccines. On a small scale, LNPs are often made using microfluidics; however, the limitations of these devices preclude their use on a large scale. The COVID-19 vaccines are manufactured in large quantities using confined impinging jet (CIJ) turbulent mixers. CIJ technology enables production at a laboratory scale with the confidence that it can be scaled to production volumes. The key concepts in CIJ mixing are that the mixing length and time scale are determined by the turbulence intensity in the mixing cavity and that the nanoparticle formation occurs away from walls, eliminating the problem of deposition on surfaces and fouling. This work demonstrates the process of making LNPs using confined impinging jet mixer technology with two geometries: the two-jet CIJ and the four-jet multi-inlet vortex mixer (MIVM). The advantages and disadvantages of each mixing geometry are discussed. In these geometries, LNPs are formed by rapid mixing of an organic solvent stream (usually ethanol containing the ionizable lipids, co-lipids, and stabilizing PEG-lipids) with an aqueous anti-solvent stream (aqueous buffer containing RNA or DNA). The operating parameters for the CIJ and MIVM mixers are presented to prepare reproducible LNPs with controlled size, zeta potential, stability, and transfection effectiveness. The differences between LNPs made with poor mixing (pipetting solutions) compared to CIJ mixing are also presented.

Effectuation, Causation and Bricolage; Entrepreneurial Orientation in the Face of Crisis, a Perspective from Developing Countries

Abstract While previous studies on individual entrepreneurial orientation have evolved more from environmental, social and cultural features, far less attention has been dedicated to personal agency factors, especially during the crisis period of post COVID-19 pandemic. Relying on personal agency theory and the entrepreneurial cognitive logic concept, this study investigates how entrepreneur’s internal locus of control affect their individual entrepreneurial orientation, particularly during periods of crisis and scarcity-post COVID-19 pandemic. Data were collected from 500 small and medium scale entrepreneurs via an online questionnaire and analyzed using partial least square (PLS-SEM) methodology. The findings show that causation, bricolage and effectuation’s affordable loss and flexibility, which are most responsive to internal locus of control, significantly impact individual entrepreneurial orientation. However, no evidence has been found on how gender, education level and education background impacts the internal locus of control to promote entrepreneurial orientation. Finally, the paper highlights the relevance of considering personal agency factors, namely internal locus of control, for policy makers, especially those involved in institutions of learning and government ministries, to boost citizens perceptions and entrepreneurial orientation and behaviour particularly in developing countries.

Synchronising an IMX219 image sensor and AS7265x spectral sensor to make a novel low-cost spectral camera

A low-cost novel spectral camera able to be used for near infrared spectroscopy was made by using a Jetson Nano to synchronize a Sony IMX219 NOIR autofocus image sensor, an AMS AS7265x 18-channel spectral sensor and Osram SFH 4737 broadband infrared LED’s. Synchronizing an image sensor and spectral sensor augments a standard RGB image with light spectrum information; capturing the light distribution information normally lost in RGB image capture. Sutherland et al. [1] used this novel spectral camera to examine the dorsal surface of juvenile lobsters as a possible pre-moult detector. Having the image and spectrum in combination allowed the incomplete and unmineralized post-moult dorsal surface to be characterized with 86.7% accuracy for the first time. A proposed application for the spectral camera is to omit the local SFH 4737 light source and use the camera in daylight, effectively making a low-cost substitute hyperspectral snapshot camera. In this configuration the camera may have application for low-cost drone deployment for small scale agriculture.

Pilot trial protocol: community intervention to improve depressive symptoms among Peruvian older adults

BackgroundNon-pharmacological interventions have proven effective at alleviating depression and anxiety symptoms in older adults. Methodological refinement and testing of these interventions in new contexts are needed on a small scale before their effectiveness and implementation can be evaluated. The purpose of this pilot study is to assess the feasibility of a future large-scale trial comparing an adapted mental health multi-component evidence-based intervention (VIDACTIVA) versus standard care for older adults experiencing depression symptoms in urban, resource-limited settings in Lima, Peru. Furthermore, this study will explore the acceptability, feasibility, and fidelity of implementing the intervention.MethodsWe will conduct an open-label, mixed methods pilot feasibility study with two parallel groups. A total of 64 older adults, stratified by sex, will be randomized at a 1:1 ratio to either the “intervention” or “control.” Participants will be followed for 22 weeks after enrollment. Those in the intervention group will receive eight VIDACTIVA sessions administered by community health workers (CHWs) over 14 weeks, with an additional eight weeks of follow-up. Participants in the control group will receive two psychoeducation sessions from a study fieldworker and will be directed to health care centers. Standard care does not involve CHWs. We will evaluate screening rates, recruitment strategies, retention rates, the acceptability of randomization, and assessments. Additionally, we will assess preliminary implementation outcomes—acceptability, feasibility, and fidelity—from the perspectives of CHWs (interventionists), older adults (main participants), older adults’ relatives, and healthcare professionals.DiscussionIf the findings from this feasibility trial are favorable, a fully powered randomized controlled trial will be conducted to evaluate `both the effectiveness and implementation of the intervention. This research will make a substantial contribution to the field of mental health in older adults, particularly by emphasizing a meticulous examination and documentation of the implementation process. By doing so, this study will offer valuable methodologies and metrics for adapting and assessing mental health interventions tailored to the unique needs of older adults in resource-constrained contexts and diverse cultural settings.Trial registrationThe current trial registration number is NCT06065020, which was registered on 26th September 2023.

Insight into the Probiogenomic Potential of Enterococcus faecium BGPAS1-3 and Application of a Potent Thermostable Bacteriocin.

This study aimed to investigate the probiogenomic features of artisanal bacteriocin-producing Enterococcus faecium BGPAS1-3 and the use of the improved pMALc5HisEk expression vector for overexpressing class II bacteriocins and the application of purified bacteriocin 31 in a milk model as a preservative against L. monocytogenes. The BGPAS1-3 strain was isolated from traditional fresh soft cheese manufactured in households on a small scale in rural locations surrounding Pale Mountain City in Bosnia and Herzegovina. The whole-genome sequencing approach and bioinformatics analyses revealed that the strain BGPAS1-3 was non-pathogenic to humans. The presence of bacteriocin operons suggested the ability of the isolate to suppress the growth of pathogens. Coding regions for three maturated bacteriocins (bacteriocin 31, bacteriocin 32, and enterocin P) produced by BGPAS1-3 were amplified and expressed in Escherichia coli ER2523 using the pMALc5HisEk system. All three bacteriocins were successfully overexpressed and purified after enterokinase cleavage but showed different antimicrobial activity. Bacteriocin 31 showed significantly stronger antimicrobial activity compared with bacteriocin 32. It was the only one that proved to be suitable for use as a food preservative against L. monocytogenes in a milk model.

Particle image velocimetry in the impeller of a centrifugal pump: Relationship between turbulent flow and energy loss

Turbulent flows play a dominant role in the operation of centrifugal pumps, which find widespread use in industrial settings and various aspects of human life. The dissipation rate of turbulent kinetic energy emerges as a key parameter within these devices, with its local values exerting a significant influence on centrifugal pump performance. Recent advances in particle image velocimetry (PIV) techniques have expanded the ability to analyze complex turbulent flows across a broad spectrum of scales. In this context, this paper aims to deepen our understanding of the turbulent flow field and its correlation with energy loss in centrifugal pump impellers. To achieve this, experiments were conducted using PIV on a transparent pump operating under different conditions. Statistics of the turbulent flow were then obtained from phase-ensemble averages of velocities, vorticity, turbulence production, and local dissipation of turbulent kinetic energy. To overcome the limited spatial resolution constraint of PIV, the large-eddy PIV (LES-PIV) method was employed to estimate the local dissipation rate. In this method, it is assumed that the motion of larger scales is measured by the PIV technique, while the smaller scales (unresolved scales) are modeled by a sub-grid scale model, calculated from the strain rate tensors obtained from the measured fields. Energy losses in the impeller were studied using two methodologies: (i) a conventional method based on power measurements, and (ii) an alternative approach based on the budget of turbulent kinetic energy. Our results reveal that turbulent loss caused by turbulence production is the main source of energy loss in the pump impeller, and it is particularly pronounced in low-flow operating conditions characterized by large-scale structures. On the other hand, in situations where flow rates exceed the best efficiency point (BEP) condition, the predominant flow structures are marked by small-scale features, mainly attributed to local dissipation of turbulence. Our findings clarify the characteristics of energy losses in centrifugal pump impellers and their relationship with the turbulent flow field, and, in addition, providing a methodology for calculating the local turbulent dissipation rate and its limitations when derived from PIV measurements.

Mud and organic content are strongly correlated with microplastic contamination in a meandering riverbed

The scale of microplastic pollution in river sediments is gradually being elucidated through an increasing number of large-scale studies. Nevertheless, microplastic distribution within a riverbed – a crucial aspect for quantification – remains poorly understood. Here we evaluate in the meandering River Lys, Belgium, how microplastic concentration varies between different sedimentary environments within the riverbed. We find that microplastic abundance is about an order of magnitude higher towards the riverbanks compared to the thalweg, corresponding with river hydrodynamics. Moreover, organic-matter and mud content are robust predictors of microplastic concentrations, apart from the outer bends, where erosion into organic-rich, muddy floodplain sediments inhibits microplastic deposition. These results increase our understanding of microplastic distribution at the small riverbed scale. They are a crucial element to guide for future sampling efforts across diverse river systems, paving the way for normalization and better quantification of microplastics trapped by river sediments and in other aquatic environments.

AngleSizer: Enhancing Spatial Scale Perception for the Visually Impaired with an Interactive Smartphone Assistant

Spatial perception, particularly at small and medium scales, is an essential human sense but poses a significant challenge for the blind and visually impaired (BVI). Traditional learning methods for BVI individuals are often constrained by the limited availability of suitable learning environments and high associated costs. To tackle these barriers, we conducted comprehensive studies to delve into the real-world challenges faced by the BVI community. We have identified several key factors hindering their spatial perception, including the high social cost of seeking assistance, inefficient methods of information intake, cognitive and behavioral disconnects, and a lack of opportunities for hands-on exploration. As a result, we developed AngleSizer, an innovative teaching assistant that leverages smartphone technology. AngleSizer is designed to enable BVI individuals to use natural interaction gestures to try, feel, understand, and learn about sizes and angles effectively. This tool incorporates dual vibration-audio feedback, carefully crafted teaching processes, and specialized learning modules to enhance the learning experience. Extensive user experiments validated its efficacy and applicability with diverse abilities and visual conditions. Ultimately, our research not only expands the understanding of BVI behavioral patterns but also greatly improves their spatial perception capabilities, in a way that is both cost-effective and allows for independent learning.

Needle-induced cavitation: A method to probe the local mechanics of brain tissue

Traditional mechanical characterization of extremely soft tissues is challenging given difficulty extracting tissue, satisfying geometric requirements, keeping tissues hydrated, and securing the tissue in an apparatus without slippage. The heterogeneous nature and structural complexity of brain tissues on small length scales makes it especially difficult to characterize. Needle-induced cavitation (NIC) is a technique that overcomes these issues and can mechanically characterize brain tissues at precise, micrometer-scale locations. This small-scale capability is crucial in order to spatially characterize diseased tissue states like fibrosis or cancer. NIC consists of inserting a needle into a tissue and pressurizing a fluid until a deformation occurs at the tip of the needle at a critical pressure. NIC is a convenient, affordable technique to measure mechanical properties, such as modulus and fracture energy, and to assess the performance of soft materials. Experimental parameters such as needle size and fluid flowrate are tunable, so that the end-user can control the length and time scales, making it uniquely capable of measuring local mechanical properties across a wide range of strain rates. The portable nature of NIC and capability to conduct in vivo experiments makes it a particularly appealing characterization technique compared to traditional methods. Despite significant developments in the technique over the last decade, wide implementation in the biological field is still limited. Here, we address the limitations of the NIC technique specifically when working with soft tissues and provide readers with expected results for brain tissue. Our goal is to assist others in conducting reliable and reproducible mechanical characterization of soft biomaterials and tissues.

Designing Supply Chain Management Pattern in Small Scale Integrated Commercial Agriculture

Designing Supply Chain Management Pattern in Small Scale Integrated Commercial Agriculture

Chronic anthropogenic disturbance causes prolific resprouting and dwarfing – A case study of a widely distributed subtropical tree

Chronic anthropogenic disturbance (CAD) comprises the additive effect of multiple anthropogenic stressors that lead to subtle but continuous alterations to the structure, composition and functioning of natural ecosystems. However, this effect has been little studied at the tree species level. Here, we examined CAD effects on Chinese beech (Fagus engleriana), a common species in northern subtropical forests that utilizes both vegetative resprouting and seeding as regenerative modes. We computed an index of CAD for each plot based on livestock grazing intensity, wood extraction and miscellaneous resource use. Over 60 20 × 20 m plots, we measured the height and DBH of a total of 1261 Chinese beech individuals (21.02 ± 13.06 per plot, [mean ± SD]), including 593 adults (9.88 ± 4.89), 576 saplings (9.60 ± 8.91) and 92 seedlings (1.53 ± 3.91), and assessed the proportions of each that exhibited resprouting (0.91 ± 0.11, 0.69 ± 0.29, and 0.09 ± 0.25, respectively). CAD was associated with a greater number of individual trees and a proliferation of stems, and with a greater proportion of resprouting seedlings, but had no effect on adult-sized stem DBH. Chinese beech thus appears generally tolerant of CAD, which may ultimately result in its increasing contribution to the maintenance of forest biomass. CAD was also associated with shorter adult and sapling stems, but taller resprouting seedling stems, implying that CAD induced dwarfism as Chinese beech matures. Further analysis showed that the proportion of resprouting was related to small scale wood extraction and miscellaneous resource use, but not to grazing. In the context of better understanding cryptic effects of CAD, our findings show that CAD can alter tree morphology and regenerative processes. These coppicing-type effects of CAD on tree morphology structure are typically associated with higher community biodiversity in managed forest coppice, and future work should investigate the biodiversity consequences of CAD at our study site. Our study shows that CAD has important implications for forest resource utilization, planning, and management, with effects on forest biomass and carbon storage in human-modified landscapes.

The root microlandscape of arbuscular mycorrhizal fungi.

Understanding the drivers of assemblages of arbuscular mycorrhizal fungi (AMF) is essential to leverage the benefits of AMF for plant growth and health. Arbuscular mycorrhizal fungi are heterogeneously distributed in space even at small scale. We review the role of plant distribution in driving AMF assemblages (the passenger hypothesis), using a transposition of the conceptual framework of landscape ecology. Because rooting systems correspond to habitat patches with limited carrying capacity that differ in quality due to host-preference effects, we suggest considering plant communities as mosaics of AMF microhabitats. We review how predictions from landscape ecology apply to plant community effects on AMF, and the existing evidence that tests these predictions. Although many studies have been conducted on the effect of plantcompositional heterogeneity on AMF assemblages, they mostly focused on the effect ofplant richness, while only a few investigated the effect of configurational heterogeneity, plant connectivity or plant community temporal dynamics. We propose key predictions and future prospects to fill these gaps. Considering plant communities as landscapes extends the passenger hypothesis by including a spatially explicit dimension and its associated ecological processes and may help understand and manipulate AMF assemblages at small spatial scales.

Axion Minicluster Streams in the Solar Neighborhood.

A consequence of QCD axion dark matter being born after inflation is the emergence of small-scale substructures known as miniclusters. Although miniclusters merge to form minihalos, this intrinsic granularity is expected to remain imprinted on small scales in our galaxy, leading to potentially damaging consequences for the campaign to detect axions directly on Earth. This picture, however, is modified when one takes into account the fact that encounters with stars will tidally strip mass from the miniclusters, creating pc-long tidal streams that act to refill the dark matter distribution. Here we ask whether or not this stripping rescues experimental prospects from the worst-case scenario in which the majority of axions remain bound up in unobservably small miniclusters. We find that the density sampled by terrestrial experiment on mpc scales will be, on average, around 70%-90% of the average local DM density, and at a typical point in the solar neighborhood, we expect most of the dark matter to be comprised of debris from O(10^{2}-10^{3}) overlapping streams. If haloscopes can measure the axion signal with high-enough frequency resolution, then these streams are revealed in the form of an intrinsically spiky line shape, in stark contrast with the standard assumption of a smooth, featureless Maxwellian distribution-a unique prediction that constitutes a way for experiments to distinguish between pre- and postinflationary axion cosmologies.

Quantum field theory and the limits of reductionism

I suggest that the current situation in quantum field theory (QFT) provides some reason to question the universal validity of ontological reductionism. I argue that the renormalization group flow is reversible except at fixed points, which makes the relation between large and small distance scales quite symmetric in QFT, opening up at least the technical possibility of a non-reductionist approach to QFT. I suggest that some conceptual problems encountered within QFT may potentially be mitigated by moving to an alternative picture in which it is no longer the case that the large supervenes on the small. Finally, I explore some specific models in which a form of non-reductionism might be implemented, and consider the prospects for future development of these models.

Prediction accuracy and repeatability of UAV based biomass estimation in wheat variety trials as affected by variable type, modelling strategy and sampling location

BackgroundThis study explores the use of Unmanned Aerial Vehicles (UAVs) for estimating wheat biomass, focusing on the impact of phenotyping and analytical protocols in the context of late-stage variety selection programs. It emphasizes the importance of variable selection, model specificity, and sampling location within the experimental plot in predicting biomass, aiming to refine UAV-based estimation techniques for enhanced selection accuracy and throughput in variety testing programs.ResultsThe research uncovered that integrating geometric and spectral traits led to an increase in prediction accuracy, whilst a recursive feature elimination (RFE) based variable selection workflowled to slight reductions in accuracy with the benefit of increased interpretability. Models, tailored to specific experiments were more accurate than those modelling all experiments together, while models trained for broad-growth stages did not significantly increase accuracy. The comparison between a permanent and a precise region of interest (ROI) within the plot showed negligible differences in biomass prediction accuracy, indicating the robustness of the approach across different sampling locations within the plot. Significant differences in the within-season repeatability (w2) of biomass predictions across different experiments highlighted the need for further investigation into the optimal timing of measurement for prediction.ConclusionsThe study highlights the promising potential of UAV technology in biomass prediction for wheat at a small plot scale. It suggests that the accuracy of biomass predictions can be significantly improved through optimizing analytical and modelling protocols (i.e., variable selection, algorithm selection, stage-specific model development). Future work should focus on exploring the applicability of these findings under a wider variety of conditions and from a more diverse set of genotypes.

Monotone Families of Circle Diffeomorphisms Driven by Expanding Circle Maps

We consider monotone families of circle diffeomorphisms forced by the strongly chaotic circle endomorphisms x↦bxmod1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$x\\mapsto bx \\mod 1$$\\end{document}, where the integer b is large. We obtain estimates of the fibered Lyapunov exponents and show that in the limit as b tends to infinity, they approach the values of the Lyapunov exponents for the corresponding random case. The estimates are based on a control of the distribution of the iterates of almost every point, up to a fixed (small) scale, depending on b.

Hierarchical Nanostructures Constructed by Soft Epitaxial Self-Assembly of Organic-Inorganic Hybrid Giant Amphiphiles.

2D nanomaterials with ångström-scale thicknesses offer a unique platform for confining molecules at an unprecedentedly small scale, presenting novel opportunities for modulating material properties and probing microscopic phenomena. In this study, mesogen-tethered polyhedral oligomeric silsesquioxane (POSS) amphiphiles with varying numbers of mesogenic tails to systematically influence molecular self-assembly and the architecture of the ensuing supramolecular structures, are synthesized. These organic-inorganic hybrid amphiphiles facilitate precise spatial arrangement and directional alignment of the primary molecular units within highly ordered supramolecular structures. The correlation between molecular design and the formation of superlattices through comprehensive structural analyses, incorporating molecular thermodynamics and kinetics, is explored. The distinct intermolecular interactions of the POSS core and the mesogenic tails drive the preferential formation of a 2D inorganic sublattice while simultaneously guiding the hierarchical assembly of organic lamellae via soft epitaxy. The findings reveal the intricate balance between shape, size, and interaction strengths of the inorganic and organic components, and how these factors collectively influence the structural hierarchy of the superstructures, which consist of multiple sublattices. By controlling this unique molecular behavior, it is possible to modulate or maximize the anisotropy of optical, mechanical, and electrical properties at the sub-nanometer scale for nanotechnology applications.