Advanced direct laser micro-structuring of polymers for optical and other applications

Excimer laser ablation is a very well researched field, and there is a vast amount of publications on this subject. Many of them focus on the fundamentals of the ablation process and try to find models to describe the ablation mechanisms. This doctoral thesis takes the existing research as basis to focus on a more applied approach. Using well-established knowledge of UV ablation of polymers this thesis presents the development of a novel technique for the ablation of repeating micro-structures into polymer surfaces. Applications for these structures include large area optical films, e.g. lenticulars for 3D effect displays.As motivation for this thesis chapter 1 gives an overview over the emerging market of advanced micro-structures for displays and novel lighting solutions. State-of-the-art methods of realising micro-structures other than by laser ablation are presented. A review of the history of UV ablation of polymers, mask imaging and industrial applications in this field lays the foundation to validate the potential of employing excimer lasers to ablate complex 3D micro-structures.In chapter 2 the so-called Synchronised Image Scanning (SIS), an advanced mask imaging technology, is introduced along with the basic hardware components. The fundamentals of SIS are presented and the evolution of the technique from simple 2D thin film patterning to complex 3D micro-structuring is described. Furthermore, the growing complexity of the mask design as well as considerations regarding the mask set-up in the system are expounded.Chapter 3 looks more closely at the required hardware and the potential in efficiency, quality and new feature geometries and compares SIS to classical mask imaging methods. For instance, it is outlined that a Step & Repeat approach is not a valid option to ablate millions of features into a surface as it would take far too long while SIS cuts down process times dramatically by its on-the-flight and parallel processing. Furthermore, a portfolio of a great variety of different 3D features realised with the SIS technology is presented.Moving on from just qualitative considerations to more quantitative investigations, chapter 4 describes how a specific micro-lens array design is realised by SIS and analysed in detail using various metrology equipment and optical performance tests. These tests reveal generally a good agreement between design and ablation result. The cause of the relatively high surface roughness of the ablated features is investigated in more detail and the influence of ablation debris on the processed features is discussed.Chapter 5 looks at artefacts created between individual scans when convex (positive) micro-structures are processed. The appearance of the artefacts is first modelled and then compared to experimental results in order to validate the model. Further it is shown which measures can be used to eliminate these artefacts.Chapter 6 presents experiments in which the surface quality is enhanced by a laser polish post process. It was found that with the right combination of fluence and number of pulses per area it is possible to reduce the RMS value from 56 nm to 12 nm.While in all the experiments in the preceding chapters the material ablated was Polycarbonate, in chapter 7 the SIS technique is applied to a wider range of polymers. It is demonstrated that by finding the etch rate data of the relevant polymers and adapting the process parameters accordingly the technique used for Polycarbonate machining is indeed transferable to other polymers as long as they show a suitable ablation behaviour.The conclusion and summary chapter 8 shows that SIS is a valid technology to produce a wide range of feature geometries on large area substrates. Enquiries from next-generation product developers in industries like displays, lighting and anti-counterfeiting show that this technology is indeed relevant for industrial applications

Advanced laser micro-structuring of super-large-area optical films

ABSTRACT A novel laser micro-machining technique to produce high density micro-structures called Synchronized Image Scanning (SIS) was introduced a couple of years ago. Over this period of time, the technique was refined in a major effort to meet the needs of various industries. There is an increasing demand for micro-structuring of large and super large area optical films, e.g. for Rear Projection TV, anti counterfeit packaging material and 3D displays. Especially in the display industry, where the screens are ever increasing in size, established micro-structuring methods like e-beam milling, diamond turning or the reflow technique struggle to keep up with the development. This paper explains how it is possible to direct laser etch hundreds of millions of lenses into a 2 m x 1.5 m substrate. It looks at the advances made in SIS in recent years regarding seam reduction, overall accuracy and precision when structuring super large area optical films, and it presents the tools and subsystems needed to generate the features in those films. Furthermore, the potential of this exciting laser micro-machining technique for rapid prototyping for all sorts of optical and non-optical structures is mapped out

Learning the Art of Instructional Conversation: The Influence of Self-Assessment on Teachers\u27 Instructional Discourse in a Reading Clinic

Over 2 decades of sociolinguistic research describe the teacher\u27s powerful role in creating the communication system that supports students\u27 learning. Yet research evidence about how to prepare and develop professionals for this role beyond their natural discourse tendencies and style remains sparse. This study examined self-assessment as a means of teacher learning that develops teachers\u27 understanding and use of discourse strategies that support instructional conversation. Using a discourse analysis tool and related procedures (transcription, analysis, and interpretation), 9 teachers examined the conceptual and social functions of their talk from videotaped excerpts of tutorial instruction over 5 weeks. Although the teachers\u27 analyses did not grow more precise, their interpretations of their talk revealed a growing ability to treat their discourse as an object of knowledge. Repeated engagement in the 3-phase self-assessment activity may have provided a form of self-assistance that promoted conceptual understanding. Design features of the self-assessment activity as a learning structure are also discussed

The Fantastic Four: A plug 'n' play set of optimal control pulses for enhancing nmr spectroscopy

We present highly robust, optimal control-based shaped pulses designed to replace all 90{\deg} and 180{\deg} hard pulses in a given pulse sequence for improved performance. Special attention was devoted to ensuring that the pulses can be simply substituted in a one-to-one fashion for the original hard pulses without any additional modification of the existing sequence. The set of four pulses for each nucleus therefore consists of 90{\deg} and 180{\deg} point-to-point (PP) and universal rotation (UR) pulses of identical duration. These 1 ms pulses provide uniform performance over resonance offsets of 20 kHz (1H) and 35 kHz (13C) and tolerate reasonably large radio frequency (RF) inhomogeneity/miscalibration of (+/-)15% (1H) and (+/-)10% (13C), making them especially suitable for NMR of small-to-medium-sized molecules (for which relaxation effects during the pulse are negligible) at an accessible and widely utilized spectrometer field strength of 600 MHz. The experimental performance of conventional hard-pulse sequences is shown to be greatly improved by incorporating the new pulses, each set referred to as the Fantastic Four (Fanta4).Comment: 28 pages, 19 figure

Change in stroke volume in response to fluid challenge: assessment using esophageal Doppler

Abstract.: Objective: To compare two methods of assessing a change in stroke volume in response to fluid challenge: esophageal Doppler and thermodilution with the pulmonary artery catheter. Design: Prospective study. Setting: Department of Intensive Care of a university medical center. Patients: 19 adult patients, intubated and sedated, with a pulmonary catheter and a clinical indication for a fluid challenge. Interventions: Two examiners independently assessed the effect of a fluid challenge on stroke volume and cardiac output with esophageal Doppler. Thermodilution performed by an independent clinician was used as the reference. Between-method variation and interobserver variability of the Doppler method were assessed. Measurements and results: There were no differences in stroke volume and cardiac output before volume challenge when measured with either of the two methods or by the two examiners using the esophageal Doppler. Despite a small bias between the methods and the two examiners using the esophageal Doppler (overall bias for cardiac output 0.3l/min), the precision was poor (1.8l/min). Conclusions: The esophageal Doppler method is a non-invasive alternative to the pulmonary artery catheter for the assessment of stroke volume in critically ill patients. Measurement of stroke volume response to fluid challenge using esophageal Doppler shows substantial interobserver variability. Despite the poor precision between methods and investigators, similar directional changes in stroke volume can be measure

Anticoagulant therapy for nodular regenerative hyperplasia in a HIV-infected patient

<p>Abstract</p> <p>Background</p> <p>Nodular regenerative hyperplasia (NRH) has been recently recognized as an emergent cause of liver disease in HIV-infected patients. NRH may cause non-cirrhotic portal hypertension with potentially severe consequences such as refractory ascites, variceal bleeding and hypersplenism. Obliteration of the small intrahepatic portal veins in association with prothrombotic disorders linked to HIV infection itself or anti-retroviral therapy seem to be the causes of NRH and thus the term HIV-associated obliterative portopathy has been proposed.</p> <p>Case Presentation</p> <p>Here we describe a case of a HIV-infected patient with biopsy-proven NRH and listed for liver transplantation (LT) because of refractory ascites and repeated upper gastrointestinal bleedings. A transjugular intrahepatic portosystemic shunt was placed as a bridge to LT and did not improve liver function. However, anticoagulant therapy with low-molecular-weight heparin (LMWH) was associated with rapid improvement in the liver condition and allowed to avoid LT in this patient.</p> <p>Conclusions</p> <p>Thus, this case underscores the relation between thrombophilia and HIV-associated NRH and emphasizes anticoagulant therapy as possible treatment.</p

Identification and weighting of the most critical "real-life” drug-drug interactions with acenocoumarol in a tertiary care hospital

Purpose: The objective of this study was to identify the most clinically relevant drug-drug interactions (DDIs) at risk of affecting acenocoumarol safety in our tertiary care university hospital, a 2,000 bed institution. Methods: We identified DDIs occurring with acenocoumarol by combining two different sources of information: a 1-year retrospective analysis of acenocoumarol prescriptions and comedications from our Computerized Physician Order Entry (CPOE) system (n = 2,439 hospitalizations) and a retrospective study of clinical pharmacology consultations involving acenocoumarol over the past 14 years (1994-2007) (n = 407). We classified these DDIs using an original risk-analysis method. A criticality index was calculated for each associated drug by multiplying three scores based on mechanism of interaction, involvement in a supratherapeutic international normalized ratio (INR) (≥ 6) and involvement in a severe bleeding. Results: One hundred and twenty-six DDIs were identified and weighted. Twenty-eight drugs had a criticality index ≥ 20 and were therefore considered at high risk for interacting with acenocoumarol by increasing its effect: 75% of these drugs involved a pharmacokinetic mechanism and 14 % a pharmacodynamic mechanism. An unknown mechanism of interaction was involved in 11 % of drugs. Conclusion: Twenty-eight specific drugs were identified as being at high risk for interacting with acenocoumarol in our hospital using an original risk-analysis method. Most analyzed drugs interact with acenocoumarol via a pharmacokinetic mechanism. Actions such as the implementation of alerts in our CPOE system should be specifically developed for these drug

Identification and weighting of the most critical "real-life” drug-drug interactions with acenocoumarol in a tertiary care hospital

Purpose: The objective of this study was to identify the most clinically relevant drug-drug interactions (DDIs) at risk of affecting acenocoumarol safety in our tertiary care university hospital, a 2,000 bed institution. Methods: We identified DDIs occurring with acenocoumarol by combining two different sources of information: a 1-year retrospective analysis of acenocoumarol prescriptions and comedications from our Computerized Physician Order Entry (CPOE) system (n = 2,439 hospitalizations) and a retrospective study of clinical pharmacology consultations involving acenocoumarol over the past 14 years (1994-2007) (n = 407). We classified these DDIs using an original risk-analysis method. A criticality index was calculated for each associated drug by multiplying three scores based on mechanism of interaction, involvement in a supratherapeutic international normalized ratio (INR) (≥ 6) and involvement in a severe bleeding. Results: One hundred and twenty-six DDIs were identified and weighted. Twenty-eight drugs had a criticality index ≥ 20 and were therefore considered at high risk for interacting with acenocoumarol by increasing its effect: 75% of these drugs involved a pharmacokinetic mechanism and 14 % a pharmacodynamic mechanism. An unknown mechanism of interaction was involved in 11 % of drugs. Conclusion: Twenty-eight specific drugs were identified as being at high risk for interacting with acenocoumarol in our hospital using an original risk-analysis method. Most analyzed drugs interact with acenocoumarol via a pharmacokinetic mechanism. Actions such as the implementation of alerts in our CPOE system should be specifically developed for these drug