Undergraduate Students’ Understanding of Surface Tension Considering Molecular Area

2020 ◽  
Vol 97 (11) ◽  
pp. 3937-3947
Author(s):  
Chulkyu Park ◽  
Chang Youn Lee ◽  
Hun-Gi Hong
Keyword(s):  
Surface Tension ◽  
Undergraduate Students ◽  
Molecular Area

MOLECULAR AREAS OF SOAPS AT THE SURFACE OF LATEX PARTICLES

1960 ◽  
Vol 38 (5) ◽  
pp. 668-680 ◽  
Author(s):  
R. J. Orr ◽  
L. Breitman
Keyword(s):  
Surface Tension ◽  
Polyethylene Oxide ◽  
Latex Particle ◽  
Molecular Area ◽  
Electron Microscopic ◽  
Latex Particles ◽  
Conventional Methods ◽  
Repulsive Forces ◽  
Microscopic Techniques ◽  
Soap Molecule

The molecular area (i.e., the area occupied by a molecule of soap adsorbed on a surface) has been determined for a number of anionic, cationic, and non-ionic emulsifiers, adsorbed on latex particles. Measurements were made by surface tension and electron microscopic techniques. The composition of the polymer did not affect the molecular area of either anionic or cationic soaps. When a mixture of non-ionic and anionic soaps was used, interaction between the soaps prevented application of the conventional methods for measuring molecular area. The interaction is manifested by a decrease in the area occupied by an anionic soap molecule which can be explained in terms of reduction in electrostatic repulsive forces between ionic soap molecules. The configuration of the polyethylene oxide chain of the non-ionic on the surface of the latex particle is deduced to be that of caterpillarlike folds.

scholarly journals Establishing the Impact of Model Surfactants on Cloud Condensation Nuclei Activity of Sea Spray Aerosols

2018 ◽  
Author(s):  
Sara D. Forestieri ◽  
Sean M. Staudt ◽  
Thomas M. Kuborn ◽  
Katharine Faber ◽  
Christopher R. Ruehl ◽  
...  
Keyword(s):  
Surface Tension ◽  
Oleic Acid ◽  
Palmitic Acid ◽  
Water Uptake ◽  
Myristic Acid ◽  
Cloud Condensation Nuclei ◽  
Sea Spray ◽  
Condensation Nuclei ◽  
Molecular Area ◽  
The Impact

Abstract. Surface active compounds present in aerosols can increase their cloud condensation nuclei (CCN) activation efficiency by reducing the surface tension (σ) in the growing droplets. However, the importance of this effect is poorly constrained by measurements. Here we present estimates of droplet surface tension near the point of activation derived from direct measurement of droplet diameters using a continuous flow stream-wise thermal gradient chamber (CFSTGC). The experiments used sea spray aerosol mimics composed of NaCl coated by varying amounts of (i) oleic acid, palmitic acid or myristic acid, (ii) mixtures of palmitic acid and oleic acid, and (iii) oxidized oleic acid. Significant reductions in σ relative to that for pure water were observed for these mimics at relative humidity (RH) near activation (~ 99.9 %) when the coating was sufficiently thick. The calculated surface pressure (π = σH2O − σobserved) values for a given organic compound or mixture collapse onto one curve when plotted as a function of molecular area for different NaCl seed sizes and measured RH. The observed critical molecular area (A0) for oleic acid determined from droplet growth was similar to that from bulk experiments conducted in a Langmuir trough. However, the observations presented here suggest that oleic acid in microscopic droplets may exhibit larger π values during monolayer compression. For myristic acid, the observed A0 compared well to bulk experiments on a fresh subphase, for which dissolution has an important impact. A significant kinetic limitation to water uptake was observed for NaCl particles coated with pure palmitic acid, likely as a result of palmitic acid being able to form a solid film. However, for binary palmitic acid-oleic acid mixtures there was no evidence of a kinetic limitation to water uptake. Oxidation of oleic acid had a minor impact on the magnitude of the surface tension reductions observed, potentially leading to a slight reduction in the effect compared to pure oleic acid. A cloud condensation nuclei (CCN) counter was also used to assess the impact on critical supersaturations of the substantial σ reductions observed at very high RH. For the fatty acid-coated NaCl particles, when the organic fraction (εorg) was > 0.90 small depressions in critical supersaturation were observed. However, when εorg 

Immunoferritin localization of intracellular antigens in positively stained frozen sections

1978 ◽  
Vol 36 (2) ◽  
pp. 168-169
Author(s):  
K. T. Tokuyasu
Keyword(s):  
Surface Tension ◽  
Water Surface ◽  
Thin Layers ◽  
The Other ◽  
Positive Staining ◽  
Frozen Sections ◽  
The Past ◽  
Ultrathin Frozen Sections ◽  
Definition Of

During the past investigations of immunoferritin localization of intracellular antigens in ultrathin frozen sections, we found that the degree of negative staining required to delineate u1trastructural details was often too dense for the recognition of ferritin particles. The quality of positive staining of ultrathin frozen sections, on the other hand, has generally been far inferior to that attainable in conventional plastic embedded sections, particularly in the definition of membranes. As we discussed before, a main cause of this difficulty seemed to be the vulnerability of frozen sections to the damaging effects of air-water surface tension at the time of drying of the sections.Indeed, we found that the quality of positive staining is greatly improved when positively stained frozen sections are protected against the effects of surface tension by embedding them in thin layers of mechanically stable materials at the time of drying (unpublished).

The Critical Point Drying Method Applied to Scanning Electron Microscopy of L-929 Cells

1970 ◽  
Vol 28 ◽  
pp. 278-279
Author(s):  
Charles TurnbiLL ◽  
Delbert E. Philpott
Keyword(s):  
Electron Microscopy ◽  
Carbon Dioxide ◽  
Surface Tension ◽  
Critical Point ◽  
Freeze Drying ◽  
Attractive Alternative ◽  
Crystal Formation ◽  
Critical Point Drying ◽  
Time Required ◽  
Scanning Electron

The advent of the scanning electron microscope (SCEM) has renewed interest in preparing specimens by avoiding the forces of surface tension. The present method of freeze drying by Boyde and Barger (1969) and Small and Marszalek (1969) does prevent surface tension but ice crystal formation and time required for pumping out the specimen to dryness has discouraged us. We believe an attractive alternative to freeze drying is the critical point method originated by Anderson (1951; for electron microscopy. He avoided surface tension effects during drying by first exchanging the specimen water with alcohol, amy L acetate and then with carbon dioxide. He then selected a specific temperature (36.5°C) and pressure (72 Atm.) at which carbon dioxide would pass from the liquid to the gaseous phase without the effect of surface tension This combination of temperature and, pressure is known as the "critical point" of the Liquid.

The Use of Styrenes as Embedding Media for Electron Microscopy

1971 ◽  
Vol 29 ◽  
pp. 488-489
Author(s):  
Edward D. De-Lamater ◽  
Eric Johnson ◽  
Thad Schoen ◽  
Cecil Whitaker
Keyword(s):  
Electron Microscopy ◽  
Surface Tension ◽  
Ultraviolet Light ◽  
Methyl Ethyl Ketone Peroxide ◽  
Methyl Ethyl ◽  
Styrene Polymerization ◽  
Radical Initiation ◽  
Tertiary Butyl ◽  
Low Viscosity ◽  
Free Radical Initiation

Monomeric styrenes are demonstrated as excellent embedding media for electron microscopy. Monomeric styrene has extremely low viscosity and low surface tension (less than 1) affording extremely rapid penetration into the specimen. Spurr's Medium based on ERL-4206 (J.Ultra. Research 26, 31-43, 1969) is viscous, requiring gradual infiltration with increasing concentrations. Styrenes are soluble in alcohol and acetone thus fitting well into the usual dehydration procedures. Infiltration with styrene may be done directly following complete dehydration without dilution.Monomeric styrenes are usually inhibited from polymerization by a catechol, in this case, tertiary butyl catechol. Styrene polymerization is activated by Methyl Ethyl Ketone peroxide, a liquid, and probably acts by overcoming the inhibition of the catechol, acting as a source of free radical initiation.Polymerization is carried out either by a temperature of 60°C. or under ultraviolet light with wave lengths of 3400-4000 Engstroms; polymerization stops on removal from the ultraviolet light or heat and is therefore controlled by the length of exposure.

The nucleation of cavities at grain boundaries

1987 ◽  
Vol 45 ◽  
pp. 288-291
Author(s):  
P. J. Goodhew
Keyword(s):  
Surface Tension ◽  
Surface Energy ◽  
Grain Boundaries ◽  
Radiation Damage ◽  
Impurity Concentration ◽  
Driving Force ◽  
Nucleation And Growth ◽  
Phase Boundaries ◽  
Cavity Nucleation ◽  
Spherical Bubble

Cavity nucleation and growth at grain and phase boundaries is of concern because it can lead to failure during creep and can lead to embrittlement as a result of radiation damage. Two major types of cavity are usually distinguished: The term bubble is applied to a cavity which contains gas at a pressure which is at least sufficient to support the surface tension (2g/r for a spherical bubble of radius r and surface energy g). The term void is generally applied to any cavity which contains less gas than this, but is not necessarily empty of gas. A void would therefore tend to shrink in the absence of any imposed driving force for growth, whereas a bubble would be stable or would tend to grow. It is widely considered that cavity nucleation always requires the presence of one or more gas atoms. However since it is extremely difficult to prepare experimental materials with a gas impurity concentration lower than their eventual cavity concentration there is little to be gained by debating this point.

Read, Understand, Learn, & Excel: Development and Testing of an Automated Reading Strategy Detection Algorithm for Postsecondary Students

2019 ◽  
Vol 28 (3) ◽  
pp. 1257-1267 ◽  
Author(s):  
Priya Kucheria ◽  
McKay Moore Sohlberg ◽  
Jason Prideaux ◽  
Stephen Fickas
Keyword(s):  
Academic Success ◽  
Undergraduate Students ◽  
Expository Text ◽  
Reading Strategy ◽  
Detection Algorithm ◽  
Expository Texts ◽  
Human Observer ◽  
Behavioral Strategies ◽  
Periodic Review ◽  
Wide Range

PurposeAn important predictor of postsecondary academic success is an individual's reading comprehension skills. Postsecondary readers apply a wide range of behavioral strategies to process text for learning purposes. Currently, no tools exist to detect a reader's use of strategies. The primary aim of this study was to develop Read, Understand, Learn, & Excel, an automated tool designed to detect reading strategy use and explore its accuracy in detecting strategies when students read digital, expository text.MethodAn iterative design was used to develop the computer algorithm for detecting 9 reading strategies. Twelve undergraduate students read 2 expository texts that were equated for length and complexity. A human observer documented the strategies employed by each reader, whereas the computer used digital sequences to detect the same strategies. Data were then coded and analyzed to determine agreement between the 2 sources of strategy detection (i.e., the computer and the observer).ResultsAgreement between the computer- and human-coded strategies was 75% or higher for 6 out of the 9 strategies. Only 3 out of the 9 strategies–previewing content, evaluating amount of remaining text, and periodic review and/or iterative summarizing–had less than 60% agreement.ConclusionRead, Understand, Learn, & Excel provides proof of concept that a reader's approach to engaging with academic text can be objectively and automatically captured. Clinical implications and suggestions to improve the sensitivity of the code are discussed.Supplemental Materialhttps://doi.org/10.23641/asha.8204786

Does a Graduate Course in Fluency Disorders Make a Difference?

2010 ◽  
Vol 20 (1) ◽  
pp. 10-14 ◽  
Author(s):  
Evelyn R. Klein ◽  
Barbara J. Amster
Keyword(s):  
Undergraduate Students ◽  
Graduate Programs ◽  
The United States ◽  
Cross Sectional Study ◽  
Sectional Study ◽  
Graduate Course ◽  
Cross Sectional ◽  
Fluency Disorders ◽  
Introductory Course ◽  
Communicative Disorders

Abstract A study by Yaruss and Quesal (2002), based on responses from 134 of 239 ASHA accredited graduate programs, indicated that approximately 25% of graduate programs in the United States allow students to earn their degree without having coursework in fluency disorders and 66% of programs allow students to graduate without clinical experience treating people who stutter (PWS). It is not surprising that many clinicians report discomfort in treating PWS. This cross-sectional study compares differences in beliefs about the cause of stuttering between freshman undergraduate students enrolled in an introductory course in communicative disorders and graduate students enrolled and in the final weeks of a graduate course in fluency disorders.

The Impact of TimeSlips on Undergraduate Students in Service Learning With Older Adults

2020 ◽  
pp. 1-8
Author(s):  
Sabine Heuer
Keyword(s):  
Older Adults ◽  
Service Learning ◽  
Undergraduate Students ◽  
Attitude Scale ◽  
Evidence Based ◽  
Attitudes Toward Older Adults ◽  
Students Attitudes ◽  
Attitude Shift ◽  
The Impact ◽  
Journal Entries

Purpose Future speech-language pathologists are often unprepared in their academic training to serve the communicative and cognitive needs of older adults with dementia. While negative attitudes toward older adults are prevalent among undergraduate students, service learning has been shown to positively affect students' attitudes toward older adults. TimeSlips is an evidence-based approach that has been shown to improve health care students' attitudes toward older adults. The purpose of this study is to explore the change in attitudes in speech-language pathology students toward older adults using TimeSlips in service learning. Method Fifty-one students participated in TimeSlips service learning with older adults and completed the Dementia Attitude Scale (DAS) before and after service learning. In addition, students completed a reflection journal. The DAS data were analyzed using nonparametric statistics, and journal entries were analyzed using a qualitative analysis approach. Results The service learners exhibited a significant increase in positive attitude as indexed on the DAS. The reflective journal entries supported the positive change in attitudes. Conclusions A noticeable attitude shift was indexed in reflective journals and on the DAS. TimeSlips is an evidence-based, patient-centered approach well suited to address challenges in the preparation of Communication Sciences and Disorders students to work with the growing population of older adults.

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