scholarly journals Controlling Droplet Marangoni Flows to Improve Microscopy-Based TB Diagnosis

Diagnostics ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 2155
Author(s):  
Stephanie I. Pearlman ◽  
Eric M. Tang ◽  
Yuankai K. Tao ◽  
Frederick R. Haselton
Keyword(s):  
Substrate Material ◽  
Marangoni Flow ◽  
Slide Surface ◽  
Microfluidic Flow ◽  
Smear Preparation ◽  
Sample Enrichment ◽  
Current Assessment ◽  
Magnetic Enrichment ◽  
Slide Area ◽  
Droplet Flows

In developing countries, the most common diagnostic method for tuberculosis (TB) is microscopic examination sputum smears. Current assessment requires time-intensive inspection across the microscope slide area, and this contributes to its poor diagnostic sensitivity of ≈50%. Spatially concentrating TB bacteria in a smaller area is one potential approach to improve visual detection and potentially increase sensitivity. We hypothesized that a combination of magnetic concentration and induced droplet Marangoni flow would spatially concentrate Mycobacterium tuberculosis on the slide surface by preferential deposition of beads and TB–bead complexes in the center of an evaporating droplet. To this end, slide substrate and droplet solvent thermal conductivities and solvent surface tension, variables known to impact microfluidic flow patterns in evaporating droplets, were varied to select the most appropriate slide surface coating. Optimization in a model system used goniometry, optical coherence tomography, and microscope images of the final deposition pattern to observe the droplet flows and maximize central deposition of 1 μm fluorescent polystyrene particles and 200 nm nanoparticles (NPs) in 2 μL droplets. Rain-X® polysiloxane glass coating was identified as the best substrate material, with a PBS-Tween droplet solvent. The use of smaller, 200 nm magnetic NPs instead of larger 1 μm beads allowed for bright field imaging of bacteria. Using these optimized components, we compared standard smear methods to the Marangoni-based spatial concentration system, which was paired with magnetic enrichment using iron oxide NPs, isolating M. bovis BCG (BCG) from samples containing 0 and 103 to 106 bacilli/mL. Compared to standard smear preparation, paired analysis demonstrated a combined volumetric and spatial sample enrichment of 100-fold. With further refinement, this magnetic/Marangoni flow concentration approach is expected to improve whole-pathogen microscopy-based diagnosis of TB and other infectious diseases.

Lithography below 100 nm

1983 ◽  
Vol 41 ◽  
pp. 96-99
Author(s):  
L. D. Jackel
Keyword(s):  
Spatial Distribution ◽  
Electron Beam ◽  
Electron Scattering ◽  
Electron Beam Lithography ◽  
Substrate Material ◽  
Local Electron ◽  
Electron Dose ◽  
Positive Resist ◽  
Exposure Process

Most production electron beam lithography systems can pattern minimum features a few tenths of a micron across. Linewidth in these systems is usually limited by the quality of the exposing beam and by electron scattering in the resist and substrate. By using a smaller spot along with exposure techniques that minimize scattering and its effects, laboratory e-beam lithography systems can now make features hundredths of a micron wide on standard substrate material. This talk will outline sane of these high- resolution e-beam lithography techniques.We first consider parameters of the exposure process that limit resolution in organic resists. For concreteness suppose that we have a “positive” resist in which exposing electrons break bonds in the resist molecules thus increasing the exposed resist's solubility in a developer. Ihe attainable resolution is obviously limited by the overall width of the exposing beam, but the spatial distribution of the beam intensity, the beam “profile” , also contributes to the resolution. Depending on the local electron dose, more or less resist bonds are broken resulting in slower or faster dissolution in the developer.

Defects in β-SiC thin films grown on α-SiC substrates

1988 ◽  
Vol 46 ◽  
pp. 568-569
Author(s):  
Karren L. More
Keyword(s):  
Thin Films ◽  
Semiconductor Device ◽  
Lattice Mismatch ◽  
Chemical Vapor ◽  
Substrate Material ◽  
Growth Interface ◽  
Si Substrates ◽  
Thermal Expansion Coefficients ◽  
Device Applications ◽  
Expansion Coefficients

Beta-SiC is an ideal candidate material for use in semiconductor device applications. Currently, monocrystalline β-SiC thin films are epitaxially grown on {100} Si substrates by chemical vapor deposition (CVD). These films, however, contain a high density of defects such as stacking faults, microtwins, and antiphase boundaries (APBs) as a result of the 20% lattice mismatch across the growth interface and an 8% difference in thermal expansion coefficients between Si and SiC. An ideal substrate material for the growth of β-SiC is α-SiC. Unfortunately, high purity, bulk α-SiC single crystals are very difficult to grow. The major source of SiC suitable for use as a substrate material is the random growth of {0001} 6H α-SiC crystals in an Acheson furnace used to make SiC grit for abrasive applications. To prepare clean, atomically smooth surfaces, the substrates are oxidized at 1473 K in flowing 02 for 1.5 h which removes ∽50 nm of the as-grown surface. The natural {0001} surface can terminate as either a Si (0001) layer or as a C (0001) layer.

Distortion in lattice-resolution scanned-probe microscope images

1993 ◽  
Vol 51 ◽  
pp. 522-523
Author(s):  
L. Fei
Keyword(s):  
Film Studies ◽  
Lattice Structure ◽  
Substrate Material ◽  
Repulsive Force ◽  
Instrument Calibration ◽  
Microscope Images ◽  
Probe Microscope ◽  
Electron Microscopes ◽  
Diffraction Patterns ◽  
Lattice Resolution

Scanned probe microscopes (SPM) have been widely used for studying the structure of a variety material surfaces and thin films. Interpretation of SPM images, however, remains a debatable subject at best. Unlike electron microscopes (EMs) where diffraction patterns and images regularly provide data on lattice spacings and angles within 1-2% and ∽1° accuracy, our experience indicates that lattice distances and angles in raw SPM images can be off by as much as 10% and ∽6°, respectively. Because SPM images can be affected by processes like the coupling between fast and slow scan direction, hysteresis of piezoelectric scanner, thermal drift, anisotropic tip and sample interaction, etc., the causes for such a large discrepancy maybe complex even though manufacturers suggest that the correction can be done through only instrument calibration.We show here that scanning repulsive force microscope (SFM or AFM) images of freshly cleaved mica, a substrate material used for thin film studies as well as for SFM instrument calibration, are distorted compared with the lattice structure expected for mica.

Microstructural characterization of YBaCuO Films on LaAlO3 substrates

1989 ◽  
Vol 47 ◽  
pp. 180-181
Author(s):  
E. L. Hall ◽  
A. Mogro-Campero ◽  
N. Lewis ◽  
L. G. Turner
Keyword(s):  
Dielectric Constant ◽  
Single Crystal ◽  
Film Growth ◽  
Microstructural Characterization ◽  
Lattice Parameter ◽  
Film Plane ◽  
Substrate Material ◽  
High Loss ◽  
Amorphous Substrates ◽  
High Dielectric

There have been a large number of recent studies of the growth of Y-Ba-Cu-O thin films, and these studies have employed a variety of substrates and growth techniques. To date, the highest values of Tc and Jc have been found for films grown by sputtering or coevaporation on single-crystal SrTiO3 substrates, which produces a uniaxially-aligned film with the YBa2Cu3Ox c-axis normal to the film plane. Multilayer growth of films on the same substrate produces a triaxially-aligned film (regions of the film have their c-axis parallel to each of the three substrate <100> directions) with lower values of Jc. Growth of films on a variety of other polycrystalline or amorphous substrates produces randomly-oriented polycrystalline films with low Jc. Although single-crystal SrTiO3 thus produces the best results, this substrate material has a number of undesireable characteristics relative to electronic applications, including very high dielectric constant and a high loss tangent at microwave frequencies. Recently, Simon et al. have shown that LaAlO3 could be used as a substrate for YBaCuO film growth. This substrate is essentially a cubic perovskite with a lattice parameter of 0.3792nm (it has a slight rhombohedral distortion at room temperature) and this material exhibits much lower dielectric constant and microwave loss tangents than SrTiO3. It is also interesting from a film growth standpoint since it has a slightly smaller lattice parameter than YBa2Cu3Ox (a=0.382nm, b=c/3=0.389nm), while SrTiO3 is slightly larger (a=0.3905nm).

A Methodology of integrated assessment of the investment attractiveness of the priority social and economic development areas

2020 ◽  
Vol 18 (4) ◽  
pp. 780-806 ◽  
Author(s):  
V.A. Yakimova ◽  
S.V. Khmura
Keyword(s):  
Integrated Assessment ◽  
Investment Risk ◽  
Methodological Issues ◽  
Investment Environment ◽  
Social And Economic Development ◽  
Analysis And Synthesis ◽  
Current Assessment ◽  
Development Area ◽  
Internal And External Factors ◽  
Advanced Development

Subject. This article deals with the theoretical and methodological issues of assessing the investment attractiveness of the advanced development areas. Objectives. The article aims to clarify the economic essence of the category Investment Attractiveness of Advanced Development Areas and related categories, and improve the methodological support to assess the investment attractiveness taking into account the characteristics of these areas. Methods. For the study, we used the methods of analysis and synthesis, generalization, analogy, classification, grouping, and systematization. Results. The article presents a methodology for assessing the investment attractiveness of the advanced development areas, taking into account indicators classified under three groups, namely investment potential, investment environment, and investment risk. It also offers recommendations to determine the type of investment attractiveness. Conclusions. Investment attractiveness, as a complex characteristic of the advanced development area, gets formed in the context of the influence of internal and external factors that are quantifiable and qualitatively assessed. To meet the needs of investors, a methodology that includes current assessment and forecasts is needed, indicating the areas of possible investment risk.

Enhancing formative feedback in orthopaedic training: Development and implementation of a competency-based assessment framework

2019 ◽  
Author(s):  
Natalie Wagner ◽  
Anita Acai ◽  
Sydney A. McQueen ◽  
Com McCarthy ◽  
Andrew McGuire ◽  
...  
Keyword(s):  
Intraclass Correlation ◽  
Formative Feedback ◽  
Assessment Practices ◽  
Tool Development ◽  
Assessment Framework ◽  
Educational Impact ◽  
Postgraduate Training Program ◽  
Current Assessment ◽  
Competency Based ◽  
Orthopaedic Training

Objective: The purpose of this study was to develop, implement, and evaluate the effectiveness of an assessment framework aimed at improving formative feedback practices in a Canadian orthopaedic postgraduate training program. Methods: Tool development began in 2014 and took place in 4 phases, each building upon the previous and informing the next. The reliability, validity, and educational impact of the tools were assessed on an ongoing basis, and changes were made accordingly. Results: One hundred eighty-two tools were completed and analyzed during the study period. Quantitative results suggested moderate to excellent agreement between raters (intraclass correlation coefficient = 0.54-0.93), and an ability of the tools to discriminate between learners at different stages of training (p’s &lt; 0.05). Qualitative data suggested that the tools improved both the quality and quantity of formative feedback given by assessors and had begun to foster a culture change around assessment in the program. Conclusions: The tool development, implementation, and evaluation processes detailed in this article can serve as a model for other training programs to consider as they move towards adopting competency-based approaches and refining current assessment practices.

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