Investigations into AFM-tip based vibration-assisted nanomachining

The recent global shortage of microchips highlighted the exponential increase in demand in the past three decades. It also showcased the fragile supply chain and its vulnerability to bottlenecking. Hence, it became evident that there is a need to explore additional manufacturing methods for miniature device manufacturing. The use of the atomic force microscope (AFM) has gained traction due to it being more environmentally friendly and its lower cost of operation when compared to other nanofabrication methods. The use of the AFM tip as a cutting tool is well established, especially when silicon workpieces are machined. In addition, the introduction of vibrations to the nanomachining process was found to provide improvements. However, the majority of research looks into silicon, with copper being investigated to a much lesser degree. Hence, this thesis investigates AFM tip-based vibration-assisted nanomachining of single crystal copper theoretically and experimentally. Following the introduction, a literature review of nanomachining is done, followed by a review regarding Atomic Force Microscopy. After that, conventional and ultraprecision machining are reviewed. Stagnation zones that play an important role at micro and nanoscales are examined. Additionally, vibration-assisted nanomachining and its various methods are explained. Also, the advantages of vibration-assisted nanomachining over conventional nanomachining are discussed. Finally, the analysis necessary for the determination of the one-direction vibration-assisted nanomachining parameter is done. Equations that govern the vibrations are explained in detail, including values extraction necessary for selecting the various frequencies and amplitudes used during experimentation. Chapter 3, in turn, studies the material deformation mechanisms at different scales and how they differ. Since the motion of dislocations is common among all size scales, it is analysed in addition to slip and the resolved shear stress. Four categories are agreed upon in the research community and are studied: (i) atomic scale, (ii) nanoscale, (iii) microscale (iv) macroscale. A brief discussion of the atomic scale is done with the inverse Hall-Petch effect on the grain size being mentioned. The nanoscale is studied in most detail due to its close relation to the experimental work of this thesis, with emphasis on nucleation of dislocations and the variations between metals and macroscopically brittle materials like silicon. After that, the microscale is discussed with its most prominent plastic deformation theory, referred to as the strain gradient plasticity (SGP). Also examined is the applicability of SGP at the nanoscale. In addition, the macroscale plastic deformation is studied, including classical theories, which in turn is followed by hardness analysis. Fatigue and specifically low-cycle fatigue are analysed then, with the impact of the size scale on the latter also reviewed. Finally, an analytical study of an experiment similar to one done in this thesis wherein proof is provided regarding the prominence of dislocation nucleation in the nanomachining of copper. As for Chapter 4, characterisation of the AFM tip shape and condition is performed. Following an introduction to tip characterisation, a review on how the shape of the tip impacts AFM operations, including nanomachining, is carried out. Methods including in-situ and ex-situ used to characterise the tip are then showcased. Later, images using the SEM are taken of the tip and later processed for tip shape extraction. Consequently, a power-law function is used to characterise the tip shape using a non-integer bluntness value. Bluntness values were extracted for both vertical and 12° tilt angle orientation, where the latter is observed in practice. Afterward, a force-displacement experiment of the same tip is done to validate the results obtained from the SEM images, using the Borodich rescaling formula. The bluntness impact of the work of adhesion and pull-off force is analysed using values extracted during experimentation, in addition to other arbitrary but practical non-integer values. In the end, an analytical study is done to investigate the factors affecting the effective rake angle. Such angle plays a vital role in the nanomachining process, including forces exerted and surface quality. However, the tip bluntness, depth of penetration, and tilt angle all impact this angle to varying degrees. Chapters 5 and 6 cover the vibration-assisted nanomachining experimental work and consequent results. Chapter 5 discusses the test setup and all the necessary equipment to complete the experiment. The cutting conditions and parameters of the tests are discussed, such as the three different amplitudes and frequencies of the vibrations resulting in nine combinations plus a conventional test used as reference. Parameters also include the cutting velocity and direction in each test and the data acquisition software settings. The chapter then briefly explains the imaging and scanning techniques used to investigate the resultant grooves. Chapter 6 discusses the outcomes and results of the experiment. The chapter starts by presenting the first test's results with no vibrations induced. Following that, the nine tests with vibrations induced are presented with specific parameters compared to the first test. These include groove depths, pile-up heights, surface roughness, chip formation, and live signal acquired from AFM nanomachining experiment. The results are then discussed, highlighting the cases where the induced vibrations did provide improvements, where they did not, and where no significant changes are noticed. Later, trends observed during testing are presented. Finally, evaluation and comparisons between the results and what is available in the research community, including theoretical and analytical studies with consequent conclusions, are presented. Finally, Chapter 7 concludes with the knowledge gaps addressed in this thesis, in both the characterisation of AFM tips as well as the optimisation of AFM tip-based vibration-assisted nanomachining and followed by a summary of the work done in this thesis and conclusions encompassing work done across the thesis. Then, suggestions regarding the additional future work that can be done to expand and improve upon what was done throughout this thesis

Management of Asymptomatic Hypertension in the Inpatient Setting.

Hypertension is common in hospitalized patients and is most often asymptomatic. While there are no guidelines for management of such patients, aggressive blood pressure treatment, including the use of intravenous antihypertensives, is often undertaken. While evidence of benefit is lacking, emerging data suggest that treatment of asymptomatic hypertension in the inpatient setting is associated with adverse outcomes, including acute kidney injury and ischemic stroke. In addition, the intensification of a preexisting antihypertensive regimen at hospital discharge significantly increases the risk of readmission without significant improvement in outpatient hypertension control. Such a combination of a common problem with the demonstrable benefit of a less aggressive approach offers considerable opportunity to improve patient care. This review article will discuss the existent literature and a specific case and make suggestions for improvement of practice

Age and gender variations in the cone-beam computed tomographic location of mandibular canal : implications for mandibular sagittal split osteotomy

Mandibular sagittal split osteotomy (MSSO) may incur unfavorable split and sensorineural injuries. Knowledge of the anatomic location of the mandibular canal (MC) and bone thickness in the region of interest for MSSO, and the possible variations by age and gender can assist in avoiding such complications. Purpose: To study the location of the MC and bone thickness in the region of MSSO by cone-beam computed tomography (CBCT) radiographs and to evaluate the possible variations by age and gender in a Jordanian population. This retrospective radio-anatomical study examined all CBCT radiographs for patients treated over three years at the University of Jordan Hospital, Amman, Jordan. Distances from the MC to the cortical external surfaces and MC diameter (MCD) were measured by a reliable observer at three predetermined regions for MSSO: region (A) [mandibular foramen area], region (B) [mandibular angle area] and region (C) [directly mesial to the second molar]. Gender and age differences in all measurements were then compared using non-parametric Mann-Whitney U test. The final study radiographs comprised a total of 202 CBCT belonged to a cohort of 202 subjects; 91 males (45.1%) and 111 (54.9%) females, with mean age (± SD) of 42.94 ± 18.54 years (range 18?90 years). Whereas only the bone thickness superior, buccal and inferior to MC in regions (B) and (C), and MCD in the three regions exhibited significant (p< 0.05) gender differences, all measured distances exhibited statistically significant (p< 0.05) differences between young and adult patients. The location of MC and bone thickness in the region of MSSO were significantly variable according to age, but exhibited sexual diamorphism only in regions (B) and (C). This fundamental knowledge should be considered during MSSO planning

Remote energy lab. Experience and improvements of european cooperation in remote labs

Due to the COVID-19 pandemic, online teaching methods have gained more interest. Most formats of teaching can be easily transferred into an online format from a technical point of view. However, this is more difficult for practical courses in a laboratory. Together with partners from three European universities, we tackled the issue of providing a practical online course for higher education levels in the framework of the EuroTeQ university. In this work, we present our concept of the course and discuss the course goals and further improvements. We tested the remote lab setting in order to offer the course on a yearly basis in future. The remote lab was focused on energy engineering and was open to students from different engineering disciplines and countries. The course was comprised of three blocks, each consisting of one lecture on the broader context of the topic and one experimental laboratory session. The experimental session was streamed via a video broadcasting service. Students were required to either deliver a written report or to write a newspaper article for each of the three blocks. The learning outcome of the course was that students on the one hand learn about the technologies discussed in the course and on the other hand learn about intercultural communication skills. The goal was to show the diversity of technologies and to show the significance of each technology for a specific country. The online experimental sessions proved to deliver a clear explanation of the topic for the students when provided with sufficient course material adapted to online formats. Contrary, keeping a high level of interaction with students during remote experiments was found most challenging

Oral Potentially Malignant Disorders among Dental Patients : a Pilot Study in Jordan

Peer reviewe

The Efficacy of Postoperative Prophylactic Antibiotics in Orthognathic Surgery: A Prospective Study in Le Fort I Osteotomy and Bilateral Intraoral Vertical Ramus Osteotomy

PURPOSE: This study examined the efficacy of the postoperative prophylactic antibiotics used in orthognathic surgery. the prevalence of surgical site infections (SSIs) was determined according to the use of postoperative prophylactic antibiotics. PATIENTS and METHODS: Fifty-six patients were divided into 2 groups. Each patient intravenously received 1.0 g of a third-generation cephalosporin (Cefpiramide) 30 minutes before surgery. Among them, 28 patients in the control group received 1.0 g Cefpiramide twice daily until the third day after surgery. the postoperative wounds were examined regularly for the presence of infectious signs. RESULTS: There was no significant difference in the incidence of postoperative wound infections between patients who had received postoperative prophylactic antibiotic administration and those who had not (p = 0.639). CONCLUSION: Prolonged prophylactic antibiotic use after orthognathic surgery may not be necessary, provided that there are no other significant factors for wound infections.ope

Reasons for choosing dentistry as a career among dental students in Saudi Arabia

Objective: This study aimed to identify reasons and influential factors for choosing dentistry as a career among dental students in Saudi Arabia. The preferred field of dental specialty following graduation will also be investigated. Materials and Methods: A questionnaire was developed and circulated among undergraduate dental students studying at a private dental college in Saudi Arabia. A list of 16 reasons that possibly influenced students’ decision to study dentistry was presented and participants were invited to indicate on a 5-point Likert scale the extent each reason influenced their choice of dentistry as a career. The listed reasons were categorized into economic, professional, vocational, social and personal reasons. Results: Totally, 788 out of 970 questionnaires were completed (response rate: 81%). Proportion of female students exceeded proportion of male students (59% and 41%, respectively) and most participants were Saudi students (73%). The top three influential factors on students’ decision to study dentistry were “Dentistry is a prestigious profession,” “I like to treat people and improve their appearance,” and “I like working with people and caring for them.” Variations were identified between male and female students and also between Saudi and non‑Saudi students in the reasons to choose dentistry as a career. The vast majority of participants (94%) expressed a desire to follow a postgraduate study. Orthodontics and oral surgery were the most preferred dental specialties. Conclusion: The social and vocational reasons were the main factors that motivated this group of dental students to attend a dental program. Greater training opportunities should be planned to accommodate the speculated increasing demand for postgraduate dental education in Saudi Arabia

Sustainable Rangeland Management Toolkit for Resilient Pastoral Systems

This toolkit is a collection of adaptable site-specific Sustainable Rangeland Management practices that developed to manage rangelands in the dry areas, achieving a neutral level of degradation and offering a strong potential to restore degraded rangelands. It is a result of collaboration among three institutions – the International Livestock Research Institute (ILRI), the International Center for Agriculture Research in the Dry Areas (ICARDA) and the International Union for Conservation of Nature (IUCN). The flexibility of the SRM toolbox within different agroecological scenarios raises its potential for upscale across the dry areas