scholarly journals Biofilm rupture by laser-induced stress waves increases with loading amplitude, independent of location

2019 ◽  
Author(s):  
Kaitlyn L. Kearns ◽  
James D. Boyd ◽  
Martha E. Grady
Keyword(s):  
Laser Fluence ◽  
Dominant Role ◽  
Film Material ◽  
Membrane Tension ◽  
Film Rupture ◽  
Laser Spallation ◽  
Straightforward Method ◽  
Membrane Effects ◽  
Substrate Surfaces ◽  
Biological Films

AbstractIntegral to the production of safe and biocompatible medical devices is to determine the interfacial properties that affect or control strong biofilm adhesion. The laser spallation technique has recently emerged as an advantageous method to quantify biofilm adhesion across candidate biomedical surfaces. However, there is a possibility that membrane tension is a factor that contributes to the stress required to separate biofilm and substrate. In that case, the stress amplitude, controlled by laser fluence, that initiates biofilm rupture would vary systematically with location on the biofilm. Film rupture, also known as spallation, occurs when film material is ejected during stress wave loading. In order to determine effects of membrane tension, we present a protocol that measures spall size with increasing laser fluence (variable fluence) and with respect to distance from the biofilm centroid (iso-fluence). Streptococcus mutans biofilms on titanium substrates serves as our model system. A total of 185 biofilm loading locations are analyzed in this study. We demonstrate that biofilm spall size increases monotonically with laser fluence and apply our procedure to failure of non-biological films. In iso-fluence experiments, no correlation is found between biofilm spall size and loading location, thus providing evidence that membrane tension does not play a dominant role in biofilm adhesion measurements. We recommend our procedure as a straightforward method to determine membrane effects in the measurement of adhesion of biological films on substrate surfaces via the laser spallation technique.Graphical Abstract

scholarly journals Evolution of the Laser-Induced Spallation Technique in Film Adhesion Measurement

2021 ◽  
Author(s):  
Hassan Ehsani ◽  
James Boyd ◽  
Junlan Wang ◽  
Martha Grady
Keyword(s):  
Stress Wave ◽  
Historical Review ◽  
High Energy ◽  
Measurement Tool ◽  
Laser Spallation ◽  
Film Adhesion ◽  
Adhesion Measurement ◽  
Wide Range ◽  
Biological Films ◽  
Film Separation

Abstract Laser-induced spallation is a process in which a stress wave generated from a rapid, high-energy laser pulse initiates the ejection of surface material opposite the surface of laser impingement. Through knowledge of the stress wave amplitude that causes film separation, the adhesion and interfacial properties of a film-on-substrate system are determined. Some advantages of the laser spallation technique are the non-contact loading, development of large stresses (on the order of GPa) and high strain rates, up to 108 /s. The applicability to both relatively thick films, tens of microns, and thin films, tens of nm, make it a unique technique for a wide range of materials and applications. This review combines the available knowledge and experience in laser spallation, as a state-of-the-art measurement tool, in a comprehensive pedagogical publication for the first time. An historical review of adhesion measurement by the laser-induced spallation technique, from its inception in the 1970s through the present day, is provided. An overview of the technique together with the physics governing the laser-induced spallation process, including functions of the absorbing and confining materials, are also discussed. Special attention is given to applications of laser spallation as an adhesion quantification technique in metals, polymers, composites, ceramics, and biological films. A compendium of available experimental parameters is provided that summarizes key laser spallation experiments across these thin film materials. This review concludes with a future outlook for the laser spallation technique, which approaches its semicentennial anniversary.

scholarly journals Physical and Chemical Interplay Between the Membrane and a Prototypical Potassium Channel Reconstituted on a Lipid Bilayer Platform

2021 ◽  
Vol 14 ◽  
Author(s):  
Masayuki Iwamoto ◽  
Shigetoshi Oiki
Keyword(s):  
Ion Channel ◽  
Potassium Channel ◽  
Molecular Mechanism ◽  
Lipid Bilayer ◽  
Membrane Tension ◽  
Potassium Channel Kcsa ◽  
Membrane Effects ◽  
Physical Features ◽  
Physical And Chemical ◽  
Specific Lipid

Once membrane potential changes or ligand binding activates the ion channel, the activity of the channel is finely modulated by the fluctuating membrane environment, involving local lipid composition and membrane tension. In the age of post-structural biology, the factors in the membrane that affect the ion channel function and how they affect it are a central concern among ion channel researchers. This review presents our strategies for elucidating the molecular mechanism of membrane effects on ion channel activity. The membrane’s diverse and intricate effects consist of chemical and physical processes. These elements can be quantified separately using lipid bilayer methods, in which a membrane is reconstructed only from the components of interest. In our advanced lipid bilayer platform (contact bubble bilayer, CBB), physical features of the membrane, such as tension, are freely controlled. We have elucidated how the specific lipid or membrane tension modulates the gating of a prototypical potassium channel, KcsA, embedded in the lipid bilayer. Our results reveal the molecular mechanism of the channel for sensing and responding to the membrane environment.

scholarly journals Biofilm and Cell Adhesion Strength on Dental Implant Surfaces via the Laser Spallation Technique

2019 ◽  
Author(s):  
J. D. Boyd ◽  
C.S. Miller ◽  
M. E. Grady
Keyword(s):  
Cell Adhesion ◽  
Dental Implant ◽  
Adhesion Strength ◽  
Laser Fluence ◽  
Cell Monolayer ◽  
Bacterial Biofilm ◽  
List Type ◽  
Laser Spallation ◽  
Titanium Substrates ◽  
Adhesion Index

AbstractObjectivesThe aim of this study is to quantify the adhesion strength differential between an oral bacterial biofilm and an osteoblast-like cell monolayer to a dental implant-simulant surface and develop a metric that quantifies the biocompatible efficacy of implant surfaces.MethodsHigh-amplitude short-duration stress waves generated by laser pulse absorption are used to spall bacteria and cells from titanium substrates. By carefully controlling laser fluence and calibration of laser fluence with applied stress, the adhesion difference between dental carry Streptococcus mutans biofilms and MG 63 osteoblast-like cell monolayers on smooth and rough titanium substrates is obtained. The Adhesion Index consists of a ratio of cell adhesion strength to biofilm adhesion strength obtaining a nondimensionalized parameter for biocompatibility assessments.ResultsAdhesion strength of 145±42 MPa is measured for MG 63 on smooth titanium, which increases to 288±24 MPa on roughened titanium. Adhesion strength for S. mutans on smooth titanium is 315±9 MPa and remained relatively constant at 332±9 MPa on roughened titanium. The Adhesion Index for smooth titanium is 0.46±0.12 which increased to 0.87±0.05 on roughened titanium.SignificanceThe laser spallation technique provides a platform to examine the tradeoffs of adhesion modulators on both biofilm and cell adhesion. This tradeoff is characterized by the Adhesion Index, which is proposed to aid biocompatibility screening and could result in improved implantation outcomes. The Adhesion Index is implemented to determine surface factors that promote favorable adhesion of cells greater than biofilms. Here, an Adhesion Index >> 1 suggests favorable biocompatibility.Graphical AbstractHighlightsBiofilm and cell monolayer adhesion are measured via the laser spallation techniqueSmooth and roughened dental implant-mimicking titanium surfaces are investigatedSurface roughness increases cell adhesion but does not alter the adhesion of biofilmsAn Adhesion Index is developed to directly quantify the adhesive competition between bacteria and cells on an implant surface

Morphologies of Nonadherent Al2O3 and Matching Substrate Surfaces

1972 ◽  
Vol 30 ◽  
pp. 524-525
Author(s):  
C. S. Giggins ◽  
J. K. Tien ◽  
B. H. Kear ◽  
F. S. Pettit
Keyword(s):  
Electron Microscopy ◽  
Oxide Scale ◽  
Oxidation Resistance ◽  
Substrate Surface ◽  
Morphological Features ◽  
Thermally Induced ◽  
Oxide Spallation ◽  
Oxidation Resistant ◽  
Induced Stresses ◽  
Substrate Surfaces

The performance of most oxidation resistant alloys and coatings is markedly improved if the oxide scale strongly adheres to the substrate surface. Consequently, in order to develop alloys and coatings with improved oxidation resistance, it has become necessary to determine the conditions that lead to spallation of oxides from the surfaces of alloys. In what follows, the morphological features of nonadherent Al2O3, and the substrate surfaces from which the Al2O3 has spalled, are presented and related to oxide spallation.The Al2O3, scales were developed by oxidizing Fe-25Cr-4Al (w/o) and Ni-rich Ni3 (Al,Ta) alloys in air at 1200°C. These scales spalled from their substrates upon cooling as a result of thermally induced stresses. The scales and the alloy substrate surfaces were then examined by scanning and replication electron microscopy.The Al2O3, scales from the Fe-Cr-Al contained filamentary protrusions at the oxide-gas interface, Fig. 1(a). In addition, nodules of oxide have been developed such that cavities were formed between the oxide and the substrate, Fig. 1(a).

Formation of high temperature phase in flash-evaporated SnSe films

1990 ◽  
Vol 48 (4) ◽  
pp. 698-699
Author(s):  
J.P.S. Hanjra
Keyword(s):  
Thin Films ◽  
Electrical Properties ◽  
Energy Gap ◽  
Dominant Role ◽  
Fine Powder ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Water Mixture ◽  
Flash Evaporation ◽  
Photovoltaic Applications

Tin mono selenide (SnSe) with an energy gap of about 1 eV is a potential material for photovoltaic applications. Various authors have studied the structure, electronic and photoelectronic properties of thin films of SnSe grown by various deposition techniques. However, for practical photovoltaic junctions the electrical properties of SnSe films need improvement. We have carried out investigations into the properties of flash evaporated SnSe films. In this paper we report our results on the structure, which plays a dominant role on the electrical properties of thin films by TEM, SEM, and electron diffraction (ED).Thin films of SnSe were deposited by flash evaporation of SnSe fine powder prepared from high purity Sn and Se, onto glass, mica and KCl substrates in a vacuum of 2Ø micro Torr. A 15% HF + 2Ø% HNO3 solution was used to detach SnSe film from the glass and mica substrates whereas the film deposited on KCl substrate was floated over an ethanol water mixture by dissolution of KCl. The floating films were picked up on the grids for their EM analysis.

Chronic Pain: Fundamental Scientific Considerations, Specifically for Legal Claims

2013 ◽  
Vol 18 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Robert J. Barth
Keyword(s):  
Health Outcomes ◽  
Pain Perception ◽  
Driving Forces ◽  
Psychological Treatment ◽  
Dominant Role ◽  
Meta Analysis ◽  
General Medicine ◽  
Pain Syndrome ◽  
Problematic Relationship

Abstract Scientific findings have indicated that psychological and social factors are the driving forces behind most chronic benign pain presentations, especially in a claim context, and are relevant to at least three of the AMA Guides publications: AMA Guides to Evaluation of Disease and Injury Causation, AMA Guides to Work Ability and Return to Work, and AMA Guides to the Evaluation of Permanent Impairment. The author reviews and summarizes studies that have identified the dominant role of financial, psychological, and other non–general medicine factors in patients who report low back pain. For example, one meta-analysis found that compensation results in an increase in pain perception and a reduction in the ability to benefit from medical and psychological treatment. Other studies have found a correlation between the level of compensation and health outcomes (greater compensation is associated with worse outcomes), and legal systems that discourage compensation for pain produce better health outcomes. One study found that, among persons with carpal tunnel syndrome, claimants had worse outcomes than nonclaimants despite receiving more treatment; another examined the problematic relationship between complex regional pain syndrome (CRPS) and compensation and found that cases of CRPS are dominated by legal claims, a disparity that highlights the dominant role of compensation. Workers’ compensation claimants are almost never evaluated for personality disorders or mental illness. The article concludes with recommendations that evaluators can consider in individual cases.

High Resolution Displacement of Functional Groups onto Fluorocarbon Resin Surface by Using ArF Excimer Laser

1996 ◽  
Vol 451 ◽  
Author(s):  
T. Shimizu ◽  
M. Murahara
Keyword(s):  
Contact Angle ◽  
High Resolution ◽  
Laser Beam ◽  
Thin Layer ◽  
Functional Groups ◽  
Excimer Laser ◽  
Laser Fluence ◽  
Large Area ◽  
Three Solutions ◽  
Arf Excimer Laser

ABSTRACTA Fluorocarbon resin surface was selectively modified by irradiation with a ArF laser beam through a thin layer of NaAlO2, B(OH)3, or H2O solution to give a hydrophilic property. As a result, with low fluence, the surface was most effectively modified with the NaAlO2 solution among the three solutions. However, the contact angle in this case changed by 10 degrees as the fluence changed only 1mJ/cm2. When modifying a large area of the surface, high resolution displacement could not be achieved because the laser beam was not uniform in displacing functional groups. Thus, the laser fluence was successfully made uniform by homogenizing the laser beam; the functional groups were replaced on the fluorocarbon resin surface with high resolution, which was successfully modified to be hydrophilic by distributing the laser fluence uniformly.

(World Wide) Work 2.0

2016 ◽  
Vol 11 (1) ◽  
pp. 91-103
Author(s):  
Carole Cusack ◽  
David Pecotic
Keyword(s):  
Open Source ◽  
World Wide ◽  
First Generation ◽  
Dominant Role ◽  
The Internet ◽  
Digital Ethnography ◽  
Beliefs And Practices ◽  
Web Presence ◽  
Theoretical Approaches ◽  
Online Engagement

The occult and the internet intersect in four ways: as a static medium for information; as a space where contested information or ideological conflict may occur; as a facilitator of communication; and as a medium for esoteric practice. The last type of activity is rare, but it is intriguing, in that technology can shape and inform beliefs and practices in unanticipated ways. Online engagement with the ‘Work’, the movement produced by the Greek Armenian spiritual teacher and esotericist G. I. Gurdjieff (c. 1866-1949) and his immediate followers, is an under-researched instance of online esoteric practice. This article addresses this scholarly desideratum, bringing the theoretical approaches of online religion and digital ethnography to bear on the Gurdjieff Internet Guide (GIG) website, founded by Reijo Oksanen (b. 1942) and later maintained by Kristina Turner, who created an accompanying Facebook page. The GIG manifests a shift away from the sectarian secrecy of the ‘Foundation’ groups, founded by Jeanne de Salzmann (1889-1990) after Gurdjieff’s death to formalise and protect the content of the Work, and the limited web presence that the Foundation permits. The GIG moves towards an ecumenical ‘open source’ approach to the dissemination of Gurdjieff’s teachings rooted in independent groups founded by other first generation followers of Gurdjieff who remained outside of the Foundation. It is argued that the deregulation of the religious and spiritual marketplace of the contemporary West, coupled with the dominant role played by the Internet in disseminating information, has radically transformed the Gurdjieff tradition, collapsing hierarchies and esoteric strategies, democratizing access for seekers, and creating new ritual and teaching modes.

POEZJA OKSYMORONU. O METAFORYCE W WIERSZACH KRASIŃSKIEGO / THE POETRY OF THE OXYMORON: ZYGMUNT KRASIŃSKI’S VERSE

2013 ◽  
Vol 54 (3) ◽  
pp. 17-27
Author(s):  
Łukasz Niewczas
Keyword(s):  
Dominant Role

Summary This re-reading of Zygmunt Krasiński’s lyrical verse rejects (at least to some extent) the generally held view of his poetry as some kind of literary fossils. To demonstrate its genuine complexity the author of this article focuses on Krasiński’s use of the oxymoron, an aspect of his poetic art that has been neglected by the critics. The oxymoron, which seems to be his favourite metaphoric device, is analysed here on the level of poetic ontology, poetic semantics, and metaphoric imagery. In each of those spheres oxymorons play a dominant role: Krasiński uses them to construct his poetic world, to complicate and problematize his meanings, and to create a highly dramatic imagery. Finally, it is argued that the shift in Krasiński’s use of the oxymoron from a sign of cleavage to that of a balanced whole corresponds to a similar evolution in his ontological views.

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