Molecular Orientation of Polymer Lubricant Films: Its Tribological Consequence

1998 ◽  
Vol 120 (2) ◽  
pp. 369-378 ◽  
Author(s):  
Chao Gao ◽  
Tam Vo ◽  
Joel Weiss
Keyword(s):  
Molecular Orientation ◽  
Energy State ◽  
Tribological Performance ◽  
Lubricant Film ◽  
Carbon Surface ◽  
Lubricant Layer ◽  
Significant Difference ◽  
End Groups ◽  
Lubricant Films ◽  
Almost All

The objective of this paper is to demonstrate, from experiments and modeling, how and why molecular orientation of functional end groups of perfluoro-polyether (PFPE) lubricants play an important role in the tribological performance of thin film magnetic disks. These disks typically have an amorphous carbon overcoat upon which a thin lubricant layer is deposited using dip-coating technique. Glancing-angle FTIR (Fourier Transform Infra-Red Spectrometry) is used for measuring molecular orientation of planer functional end groups. A molecular orientation index (MOI) was defined as 1 for randomly oriented functional end groups. The MOI is mathematically derived as 3 (maximum) for lubricant molecules oriented with their functional end groups perpendicular to the surface, and as 0 (minimum) if lubricant molecules oriented with their functional end groups parallel to the surface. The MOI is shown to depend on processing conditions and lubricant film thickness. The tribological performance of the lubricant films was evaluated using drag-mode contact start-stop testing. It was found that wear durability of the lubricant films (~2 nm) with MOI ~ 1.5 is a few times better than those with MOI ~ 0.5 to 1.0. No significant difference in the amount of bonded lubricant film was detected over the range of MOI studied. Nor was there a detectable relationship with hydrophobicity. It was inferred from decreased MOI values due to thermal effects and storage time that a smaller MOI value corresponds to a lower free energy state of the lubricant film. Interestingly, MOI values for bonded lubricant films for Process A are found to be close to 3.0, suggesting that almost all functional end groups in the bonded films are oriented perpendicular to the carbon surface, close to 2.0 for process B, and close to 0 for process C, meaning that almost all functional end groups in the bonded films from process C are oriented parallel to the carbon surface. Relationship between physical/chemical bonding configurations and MOI values are graphically presented in detail. Based on this relation, a simple model on lubricant film structures for the three processes studied is presented. The model MOI values agree very well with measured MOI values as a function of lubricant thickness for all three processes, and the model also appears to account for the observed tribology performance for the MOI values studied (0.5 ~ 1.5).

Transformative Learning in Mastery-Oriented CS0 Course

2021 ◽  
pp. 234763112110072
Author(s):  
Srinivasan Lakshminarayanan ◽  
N. J. Rao ◽  
G. K. Meghana
Keyword(s):  
Transformative Learning ◽  
First Year ◽  
Guided Discovery ◽  
Engineering Programs ◽  
Transformative Experiences ◽  
Significant Difference ◽  
Cognitive Levels ◽  
Almost All ◽  
Core Course

The introductory programming course, commonly known as CS1 and offered as a core course in the first year in all engineering programs in India, is unique because it can address higher cognitive levels, metacognition and some aspects of the affective domain. It can provide much needed transformative experiences to students coming from a system of school education that is dominantly performance-driven. Unfortunately, the CS1 course, as practiced in almost all engineering programs, is also performance-driven because of a variety of compulsions. This paper suggests that the inclusion of a course CS0 can bring about transformative learning that can potentially make a significant difference in the quality of learning in all subsequent engineering courses. The suggested instruction design of this course takes the advantage of the unique features of a course in programming. The proposed CS0 course uses “extreme apprenticeship” and “guided discovery” methods of instruction. The effectiveness of these instruction methods was established through the use of the thematic analysis, a well-known qualitative research method, and the associated coding of transformative learning experiences and instruction components.

Do Deeper Levels of Cervical Biopsies Preceded by a Pap Smear Diagnosis of LSIL, ASCUS, or NILM/HPV+ Increase the Yield of Identifying Clinically Significant Lesions?

2020 ◽  
Vol 154 (Supplement_1) ◽  
pp. S163-S164
Author(s):  
K G Manjee ◽  
W G Watkin
Keyword(s):  
Pap Smear ◽  
Past History ◽  
Prior History ◽  
Cervical Biopsy ◽  
P16 Immunohistochemistry ◽  
Hpv Status ◽  
Significant Difference ◽  
History Of ◽  
Clinically Significant ◽  
Almost All

Abstract Introduction/Objective Cervical biopsy is performed following an abnormal pap smear or positive HPV testing in an attempt to uncover clinically significant lesions [HSIL/invasive carcinoma (HSIL+)]. An excisional procedure is considered if biopsy confirms HSIL+. When preceded by pap smear of LSIL, ASCUS, NILM/HPV+ or persistent HPV, continued surveillance is recommended for biopsies showing no SIL or LSIL. In our laboratory, cervical biopsies are routinely sectioned at 3 levels. Deeper levels are often ordered when initial sections are non-diagnostic. p16 immunohistochemistry, with or without deeper levels, is often ordered to confirm HSIL, or to differentiate HSIL from mimics. In this study, we examine whether and in what clinical situations does obtaining additional levels uncover clinically significant lesions. Methods 430 cervical biopsies between January-May 2018, with recent cytology of LSIL, ASCUS or NILM/HPV+ were identified in the pathology database. HPV status (if known), final biopsy diagnosis and past history of LSIL/HSIL were recorded. For each biopsy, orders for additional levels and/or p16 immunohistochemistry were recorded resulting in 4 categories: C1-no additional levels or p16, C2-deeper only, C3-deeper+p16 and C4-p16 only. Final diagnoses were divided into HSIL+, LSIL and no SIL. Results There was no significant difference in prior history of LSIL/HSIL and HPV status between all categories. Biopsy results were as follows: HSIL+: 11/222 (5%) C1; 1/78 (1%) C2; 7/43 (16%) C3; 15/87 (17%) C4 LSIL: 91/222 (41%) C1; 7/78 (9%) C2; 16/43 (37%) C3; 35/87 (40%) C4 No SIL: 120/222 (54%) C1; 70/78 (90%) C2; 20/43 (46%) C3; 37/87 (42%) C4 The average number of additional levels in C2 and C3 was 3.8 and 1.8, respectively. Conclusion Deeper levels alone did not enhance the detection of HSIL+. Almost all LSIL/HSIL were detected when initial levels were diagnostic or suspicious and supported by p16 immunohistochemistry. 3 levels are adequate to detect clinically significant lesions.

scholarly journals RT-PCR analysis of Deformed wing virus in honeybees (Apis mellifera) and mites (Varroa destructor)

2005 ◽  
Vol 86 (12) ◽  
pp. 3419-3424 ◽  
Author(s):  
Constanze Yue ◽  
Elke Genersch
Keyword(s):  
Varroa Destructor ◽  
Pcr Analysis ◽  
Body Parts ◽  
Rt Pcr ◽  
Larval Food ◽  
Viral Pathogen ◽  
Deformed Wing Virus ◽  
Significant Difference ◽  
Almost All ◽  
Viral Sequences

Deformed wing virus (DWV) is a honeybee viral pathogen either persisting as an inapparent infection or resulting in wing deformity. The occurrence of deformity is associated with the transmission of DWV through Varroa destructor during pupal stages. Such infections with DWV add to the pathology of V. destructor and play a major role in colony collapse in the course of varroosis. Using a recently developed RT-PCR protocol for the detection of DWV, individual bees and mites originating from hives differing in Varroa infestation levels and the occurrence of crippled bees were analysed. It was found that 100 % of both crippled and asymptomatic bees were positive for DWV. However, a significant difference in the spatial distribution of DWV between asymptomatic and crippled bees could be demonstrated: when analysing head, thorax and abdomen of crippled bees, all body parts were always strongly positive for viral sequences. In contrast, for asymptomatic bees viral sequences could be detected in RNA extracted from the thorax and/or abdomen but never in RNA extracted from the head. DWV replication was demonstrated in almost all DWV-positive body parts of infected bees. Analysing individual mites for the presence of DWV revealed that the percentage of DWV-positive mites differed between mite populations. In addition, it was demonstrated that DWV was able to replicate in some but not all mites. Interestingly, virus replication in mites was correlated with wing deformity. DWV was also detected in the larval food, implicating that in addition to transmission by V. destructor DWV is also transmitted by feeding.

Study of Direct Measuring of Lubricant Condition in Rolling Element Bearings With Microcomputer Technique

1990 ◽  
Vol 112 (1) ◽  
pp. 92-97 ◽  
Author(s):  
Dongchu Zhao
Keyword(s):  
Film Thickness ◽  
Strain Gage ◽  
Lubricant Film ◽  
Rolling Element Bearings ◽  
Main Program ◽  
Test Apparatus ◽  
Lubricant Film Thickness ◽  
Rolling Element ◽  
Lubricant Films ◽  
Flow Charts

A method for measuring the lubricant condition with strain gage in rolling element bearings and the instrument used are introduced. In order to illustrate the method and the instrument, the theory of measuring lubricant films in rolling element bearings using strain technique, test apparatus, microcomputer hardware as well as software, flow charts for the main program and subprograms, are first described in detail. In addition, the lubricant film thickness is measured for several different lubricants and results are compared with theoretical ones. It is demonstrated that using the method and the instrument introduced in this paper, one can measure the lubricant condition inside bearings very accurately.

Quantification of the Surface Morphology of Lubricant Films With Polar End Groups Using Molecular Dynamics Simulation: Periodic Changes in Morphology Depending on Film Thickness

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Susumu Ogata ◽  
Hedong Zhang ◽  
Kenji Fukuzawa ◽  
Yasunaga Mitsuya
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Surface Morphology ◽  
Film Thickness ◽  
Film Surface ◽  
Dynamics Simulation ◽  
Molecular Probe ◽  
Coarse Grained ◽  
End Groups ◽  
Lubricant Films

Using a coarse-grained molecular dynamics simulation based on the bead-spring polymer model, we reproduced the film distribution of molecularly thin lubricant films with polar end groups coated on the disk surface and quantified the film-surface morphology using a molecular-probe scanning method. We found that the film-surface morphology changed periodically with increasing film thickness. The monolayer of a polar lubricant that entirely covers the solid surface provides a flat lubricant surface by exposing its nonpolar backbone outside of the monolayer. By increasing film thickness, the end beads aggregate to make clusters, and bulges form on the lubricant surface, accompanying an increase in surface roughness. The bulges continue to grow even though the averaged film thickness reaches or exceeds the bilayer thickness. With further increases in film thickness, the clusters start to be uniformly distributed in the lateral direction to clearly form a third layer. As for the formation of fourth and fifth layers, the process is basically the same as that for the second and third layers. Through our calculations of the intermolecular potential field and the intermolecular force field, these values are found to change periodically and are synchronized with the formation of molecule aggregations, which explains the mechanism of forming the layered structure that is inherent to a polar lubricant.

scholarly journals DIFFERENT APPROACHES OF CLIENTS AND CONSULTANTS TO CONTRACTORS’ QUALIFICATION AND SELECTION

2005 ◽  
Vol 11 (4) ◽  
pp. 267-276 ◽  
Author(s):  
Mehmedali Egemen ◽  
Abdulrezak N. Mohamed
Keyword(s):  
Construction Industry ◽  
Selection Processes ◽  
Significant Difference ◽  
Different Types ◽  
Almost All ◽  
High Willingness

Nowadays, clients are the dominant groups in almost all types of industries. However, the construction industry is unique and consultants, as representatives of clients, are very important figures in this industry as well. By presenting survey findings of 91 clients and 50 consultants, this study reveals clients’ and consultants’ differing expectations of contracting organisations during contractor qualification and selection. The study has clearly confirmed the fact that consultants’ perspectives are rather different and their contractors’ expectations of their clients vary very significantly from the clients themselves. Furthermore, significantly different results were found even among different types of consultants and different categories of clients. Moreover, this study showed that both clients and consultants had high willingness to continue working with the same contractor in possible future works assuming they are satisfied with the previous works. The criteria, which contribute to achieving full client and/or consultant satisfaction and hence lead to possible repetitive works are identified and the results showed the existence of significant difference between clients and consultants perspectives regarding this issue as well. The framework presented within this paper aims to help the contracting organisations to compare and recognise the different approaches and perceptions of both clients and consultants during contractor qualification and selection processes. The contracting organisations in the related sectors will be able to use the framework provided within this study to recognise the overall demand in a more complete and better manner and hence formulate or modify strategies accordingly.

scholarly journals Evaluation of the relationship between MIH severity and dental fear among the children

2019 ◽  
Vol 6 (10) ◽  
pp. 284-287
Author(s):  
Can Özükoç
Keyword(s):  
Behavioral Problems ◽  
Dental Anxiety ◽  
Pediatric Dentistry ◽  
Dental Fear ◽  
Common Condition ◽  
Molar Incisor Hypomineralization ◽  
Significant Difference ◽  
Fear Survey Schedule ◽  
Almost All ◽  
The Relationship

Objective: Molar incisor hypomineralization (MIH), a quite common condition in pediatric dentistry, whose treatment might seem complicated, manifests itself with severe dental anxiety and fear that can cause behavioral problems. Although dental fear is seen in almost all cases, it is believed that dental fear will increase as the severity of MIH increases. This study evaluates the relationship between MIH severity and dental fear. Material and Methods: Children Fear Survey Schedule-Dental Subscale (CFSS-DS) was used to measure dental fear in 58 (51.79%) children whose teeth suffered from mild, moderate or severe MIH and 54 (48.21%) children with healthy teeth. Scores between 1 (not afraid at all) and 5 (very afraid) were given according to the responses. Each question was evaluated separately in order to obtain the total score. Results: Children with severe MIH who participated in the study were proved to be more afraid of the dentists, drill sounds, injections, placement of instruments in the mouth, choking and going to the hospital; and there was a statistically significant difference (p<0.05). Conclusion: Although it was observed that the severity of MIH and dental fear are correlated and dental fear increases with the increase in the MIH severity, further studies in this subject are necessary.

scholarly journals Struktur Komunitas Rumput Laut di Perairan Pasir Panjang Desa OlibuuKabupaten Boalemo, Gorontalo

2018 ◽  
Vol 7 (1) ◽  
pp. 59
Author(s):  
Edi Wibowo ◽  
Raden Ario ◽  
Suryono Suryono ◽  
Nur Taufiq ◽  
Destalino Destalino
Keyword(s):  
Diversity Index ◽  
Survey Methods ◽  
Species Abundance ◽  
Brown Seaweed ◽  
Sample Survey ◽  
Research Station ◽  
Water Medium ◽  
Significant Difference ◽  
Index Value ◽  
Almost All

Rumput laut atau seaweed termasuk tumbuhan berthallus yang banyak dijumpai hampir di seluruh pantai Indonesia, terutama wilayah pantai yang mempunyai rataan terumbu karang.  Perbedaan mendasar sistem hidupnya dengan tumbuhan darat adalah dalam pengambilan zat-zat makanan. Tumbuhan darat sangat bergantung pada akar sebagai alat pengambil/ penyerap zat hara dari substrat, sedangkan rumput laut menyerap zat hara yang dibutuhkan bagi pertumbuhannya dari medium air dengan cara difusi melalui permukaan substansi fisiknya.Penelitian ini bertujuan untuk mengetahui struktur komunitas rumput laut di perairan Pasir Panjang Pulau Limbah, Kecamatan Paguyaman Pantai, Kabupaten Boalemo, Provinsi Gorontalo. Metoda penelitian yang digunakan adalah bersifat diskriptif.Adapun pengumpulan data dilakukan dengan metode sample survey methods. Hasil penelitian menunjukan bahwa perairan Pulau Limbah di dominasi oleh Rumput Laut Coklat dengan kelimpahan tertinggi Padina australis. Nilai Indeks Keanekaragaman (H’) Rumput Laut tertinggi terdapat pada stasiun C dengan nilai rerata: 1,854 dan yang terendah pada Stasiun A dengan nilai rerata: 1,469. Nilai Indeks Keseragaman (E)  nilai tertinggi terdapat pada Stasiun C dengan nilai rerata: 0,679 dan terendah pada stasiun A dengan nilai rerata: 0,668. Nilai indeks Dominansi (C) tertinggi terdapat pada Stasiun A dengan nilai rerata : 0,251 dan nilai terendah stasiun B dengan nilai rerata: 0,187. Analisis Ragam (Anova) menunjukan bahwa stasiun penelitian memberikan perbedaan yang nyata (P≤0,05) terhadap nilai Indeks Keanekaragaman (H’), Indeks Keseragaman (E) serta Indeks Dominasi (C).  Seaweed including thallus plants that are found almost all over the coast of Indonesia, especially on beaches that have coral reefs. Seaweed is a photosynthetic organism as well as plants on land. The fundamental difference of his life system is in the taking of food substances. Ground plants realy heavily on roots as a nutrient removal device from the substrate, while seaweed absorbs the nutrients needed for its growth from the water medium by diffusion through the surface of its physical substance. This study aims to determine the structure of seaweed communities in Limbah Island Waters, District Paguyaman Beach. The results showed that the waters of Limbah Island is dominated by brown seaweed with the highest species abundance was Padina australis. The highest index value of Seaweed diversity (H’) was found at station C with average: 1,854 and the lowest at station A with a mean of: 1,469. For uniformity index value (E) the highest value is at station C with average: 0,679 and the lowest at station A with a mean of: 0,668. The highest index value of dominance (C) is at station A with a mean of: 0,251 and the lowest value at station B with a mean of: 0,187. The result of the analysis of variance (Anova) showed that the research station give a significant difference (P≤0,05) to the Diversity Index (H’), Uniformity Index (E) and Domination Index (C).

scholarly journals SMOKING GENOTOXICITY IN PERIPHERAL BLOOD LYMPHOCYTES USING THE COMET ASSAY

2013 ◽  
Vol 03 (03) ◽  
pp. 038-041
Author(s):  
Shobha S. Shetty ◽  
Hrishikesh Nachane
Keyword(s):  
Dna Damage ◽  
Comet Assay ◽  
Peripheral Blood ◽  
Peripheral Blood Lymphocytes ◽  
The Body ◽  
P Value ◽  
Tail Moment ◽  
Blood Lymphocytes ◽  
Significant Difference ◽  
Almost All

Abstract Background: Smoking has been shown to have a positive effect on DNA damage in almost all the cells of the body. Quantitative analysis of this damage will help in assessing the etiopathogenesis of various nicotine induced damage to the body. Comet assay has been an emerging tool in this regard and hence was applied by us to estimate the severity of DNA damage in smokers. Aims & Objectives: To evaluate the DNA genotoxicity in peripheral blood lymphocytes in smokers and their comparison with non smokers & assess the quantitative damage. Materials and methods: 30 smokers & 20 non smokers were recruited & their peripheral blood was taken for the comet assay to look for Olive moment & Tail moment to quantitatively assess the DNA damage due to cigarette smoking. Results: In our study there was no significant difference in the analysis of DNA damage (with regard to tail moment & olive moment) in smokers versus non smokers (P value: more than 0.05). Conclusions: Though smoking is known to cause DNA damage, we did not find significant differences between the two groups probably due to other multifactorial etiologies for genotoxicity.

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