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Glaciers in the Himalaya–Karakoram mountain ranges harbour approximately half of the ice volume in High-mountain Asia and modulate the flow of freshwater to almost 869 million people within the Indus, Tarim, Ganges and Brahmaputra river basins. Since the mid-twentieth century, rising temperatures have led to unsustainably high melting rates for many glaciers, particularly in the Himalaya, temporarily increasing summer meltwater run-off but continuously reducing the ice-storage volume. In this Review, we discuss how and why glaciers and meltwater supplies have changed, how they will likely evolve in the future and how these changes impact water resources and water-related hazards. Heterogeneous glacier retreat is changing streamflow patterns, in turn, affecting the incidence of glacial-lake outburst floods and exacerbating the risk of flooding and water shortages associated with future climate change. These changes could negatively impact downstream populations and infrastructure, including the thriving hydropower sector and some of the world’s largest irrigated agriculture systems, by making water flow more extreme and unpredictable. An improved in situ monitoring network for weather, hydrology and glacier change is a crucial requirement for predicting the future of this resource and associated hazards, and their impact on regional water, energy and food security. Glaciers in the Himalaya and Karakoram mountain ranges provide freshwater and hydropower to millions of people but are also melting at unsustainably high rates. This Review discusses recent and projected changes in glacier melt and resulting implications for regional water-related hazards and water resources.

Southwest China plays a key role in global hydropower; its current installed capacity is roughly equal to that of the rest of Asia. This immense hydropower capacity stems from some of the world’s largest dams as well as the world’s greatest density of smaller projects. However, our knowledge about the region’s hydropower utilisation patterns and spatio-temporal impacts is based on limited empirical data. This chapter provides a detailed analysis of the uneven spatio-temporal hydropower development in the area and the fluctuating oversupply of hydroelectricity. While as of 2019 hydropower development is advanced in Sichuan (77 GW, 316 TWh) and Yunnan (64 GW, 270 TWh), it is still in an early stage in Tibet. However, Tibet’s hydropower development might even surpass both provinces in the future. The second part of the chapter analyses the utilisation of hydroelectricity, with an emphasis on Yunnan. Our analysis focuses on the trade-offs (benefits, disadvantages, and current trends) related to large-scale power exports to coastal load centres, mapping out these exports for all of Southwest China. Further, we discuss the unique role of power-intensive industries within Yunnan and the impacts of rural electrification on local utilisation of hydropower.

Axial cracking inspections have become common place on a global level within pipeline operator’s integrity management programs. As technology continues to improve, operators are presented with more accurate assessments of the assets that are in current operation. However as more information is collected more threats are being identified and need to be assessed in a manner that is more applicable to their specific morphology. It is well known that vintage ERW manufacturing techniques can suffer from a wide range of potential threats such as lack of fusion or inclusions within the steel forming hook cracks during the rolling and welding process. Current In-line inspection technologies that are designed to detect, Identify and size cracklike flaws in pipelines are very proficient at doing so. However, due to the physical principals of the Ultrasonic pulse echo technology, deep features approaching, or above pulse echo saturation amplitudes pose challenges in determining accurate depth sizing. In 2015 a Canadian pipeline operator determined the need to inspect one of their 16” assets for axial crack-like indications. During the analysis of this inspection data set, a number of saturated crack-like indications were reported. Saturated cracklike signals present a challenge to operators as they have to be considered in a conservative manner as 4mm or deeper which in turn leads to difficulties in the prioritization of resources associated with the excavation program. The operator approached NDT Global in 2017, after the release of NDT Global’s Enhanced sizing depth algorithm to reevaluate the features that were present in the previous crack inspection data set. Working together with the operator, NDT Global applied the Enhanced sizing methodology to all features of significance in the pipeline segment and compared the results to lab measurements and in field NDE measurements. The outcome of the reanalysis using the most up to date software algorithms utilizing enhanced sizing showed great benefits by increasing the accuracy of the crack depth sizing as NDT Global was now able to report full through wall depth sizing, however there were still some limitations on the ability to accurately size crack-like features as the primary threat is believed to be a result of hook cracks. As a final step in this program NDT Global was provided sample spools that were cut out of the pipeline segment to perform a pull testing campaign utilizing the newest crack detection technology that was specifically targeted towards accurately sizing tilted and skewed crack like features. The authors will briefly discuss the pipeline system and inspection campaign and in detail will discuss the benefits of using technology that has been developed to help pipeline operators better understand the threats in their integrity management program.

Pipeline operators use different approaches, often in combination, to ensure the safe operation of an asset. Historically, hydrostatic testing is the most accepted methodology for assessing critical flaws in a pipeline system, achieved by stressing the pipeline above the standard operating limits. By design, a release during this test removes a critical flaw from the system. There are significant drawbacks to this type of assessment. Such drawbacks include high costs of implementation, feature growth, previously blunt defects sharpening and system downtime. Driven by the operator (Marathon Pipe Line) to investigate alternative approaches, a consortium of (4) parties formed to develop and validate an alternative and enhanced solution. The research and execution of the project was structured in (4) phases. • Phase I — Determine which crack morphologies are challenging to ILI technology in terms of detection and depth determination and test initial improvements to ILI technology. This included loop testing improved crack detection ILI robots and destructive assessment with pipe samples to identify gaps in ILI technology and analysis techniques. • Phase II — Assess vendor improved ILI technology on the operating pipelines using advanced in the ditch non-destructive evaluation (NDE) methods and destructive testing of pipe samples from the pipelines. Identify the additional improvements if necessary. • Phase III — Implement specific improvements to ILI technology that are completed based on Phase I and II results. Validate the new ILI platform on the specific pipeline. • Phase IV — Determination whether the new ILI platform can provide equivalent pipe seam system reliability to hydrostatic testing. A probabilistic approach will be used that would account for the expected statistical distribution of pipe properties, fatigue crack growth rates, position along the pipeline, and flaw sizes. This paper is a summary of the research and work for this ILI In Lieu of a Hydrostatic Testing initiative.

Cracks in dents or linear anomalies interacting with dents are a major pipeline threat. These combined anomalies represent challenges to the Mechanical Engineers that design ILI tools as they need to keep the sensor in an optimal position towards the inner pipe wall. Ultrasonic Crack (UC) tools consist in a sensor plate with a fixed incidence angle that depends on the coupling medium. This plate is then attached to the skids; these are in constant contact with the internal pipe wall. When the tool interacts with a dent, the incidence angle is not optimal; therefore, detection of any interacting feature is compromised. By not having the optimum angles in the pipe wall, the amplitudes from the reflections caused by cracks will be attenuated. Depending on the magnitude of the attenuation, these might be below analysis thresholds meaning that an algorithm and/or analyst will not consider them as relevant signals. Up to this point, detection of interacting features sounds like a “guess “ or “luck”. So, how can we use UC inspection to detect the interacting features? How can operators manage their assets knowing that they have dents but there is an uncertainty if there are interacting features? To answer these questions, a systematic approach had to be used. It consisted of multiple phases where 1.- The mechanical design of the tool was understood, 2.- Simulation campaigns to understand the ultrasonic pulse while interacting with the dent, 3.- Pump tests with artificial features, and 4.- Pump test with real features. All of the data gathered through the different phases allowed the authors to understand the attributes from the features and conditions that influence detection and identification of cracks in dents. This derived in a performance specification stating the truth capabilities to detect interacting features in a dent. These learnings were applied to commercial inspections where the feedback loop is closed with the field verifications.

Small hydropower (SHP) has a global reputation as a ‘green’, low-carbon energy source that improves rural livelihoods and contributes to local economic development. In China, SHP has grown rapidly since the early 2000s, particularly in the water-rich provinces in the country’s southwest. However, because SHP plants in China are privately-operated and approved by local governments, there is an incentive to construct large, multiple-cascade systems to generate as much power as possible. In many areas, this has led to over-development of SHP and associated negative environmental and social impacts. In this paper, we identify the factors that shape geographies of SHP over-development, what we refer to as ‘shades’ of green energy. We then analyze the direct and indirect impacts of over-development. We draw on interviews and electricity generation data from six prefectures in Yunnan province, one of the world’s largest hydropower producing regions. We find that prefectures that operate in a semi-autonomous way in electricity management and industrial planning are most prone to over-develop SHP, since they depend on hydropower revenues from electricity generation and local energy-intensive industries. We also find that over-development of SHP causes streamflow reductions and unstable electricity generation, and in some areas, drives an increase in environmentally-destructive mineral processing and reduces irrigation water access. These findings suggest a need for coordinated river basin planning on small watersheds and a reassessment of the role of SHP in local economic development.

The Ayeyarwady basin, one of Asia's largest transnational river basins, shared by Myanmar, China and India, has an immense theoretical hydropower potential of 45 GW. Currently hydropower projects with an approximate capacity of 33 GW are already in various stages of development. Projects include some of the world's largest and most controversial endeavours (e.g. Myitsone). Of these projects 6.4 GW are already installed in 187 hydropower projects (≥1 MW). Despite its huge relevance, the transnational Ayeyarwady basin still belongs to the less known basins, which is largely attributed to its small Chinese section. However, the current knowledge is limited to Myanmar's segment where a limited number of 16 projects exist. In contrast, there are a multitude of projects −174 (18 large and 156 small) - in the Chinese section, including the basins largest one (Daying-4: 875 MW). The combination of small and large projects makes the Chinese section one of the most dense (small) hydropower catchments worldwide. About half of the entire basin's hydropower output is exported to the energy starved Guangdong province (from both countries) and almost another quarter is used for energy intensive industries in the tiny Chinese section; hence currently only about 30% of the basin's generated (hydro-)electricity is used there for households, industry, etc. This results in a complex water-energy nexus that is complicated by a tangled geopolitical setting directly in the border region, where many projects are located. This paper describes that nexus based on Darrin Magee's powershed approach.

Since the late 1980’s Ultrasonic tools have been used for the detection and sizing of crack like indications. ILI service providers developed inspection technologies for liquid and gas lines that are widely used nowadays. In comparison to axial cracking, circumferential cracking is not a prevalent risk to most pipelines and therefore is not as well understood. Nevertheless, pipeline Operators observe from time to time circumferentially oriented defects, often in combination with circumferential welds or local stress/strain accumulations. These are often caused by pipeline movement, which may especially occur in mountain areas. With the introduction of Ultrasonic circumferential crack inspection tools in the late 2000’s the knowledge has steadily increased over time. Extensive data collected from in-ditch NDE validations has provided NDT Global with an increased knowledge of the morphology of single cracking and stress corrosion cracking defects both in the axial and circumferential orientations. Field verifications have shown that not all features have the same morphology. Some of the challenges with circumferential cracking are for features that fall outside of the industry standard specifications. These types of features can exhibit characteristics such as being sloped, skewed or tilted. In 2016 NDT Global was approached by Plains Midstream Canada to complete inspections utilizing the 10″ Ultrasonic Circumferential crack inspection technology. The pipeline system spans 188km within Canada and consists of 2 segments. The pipeline traverses several elevation changes and crosses several creeks and roads. Circumferential cracking was identified during dig campaigns performed for other threats, therefore the need to inspect each pipeline segment with the Ultrasonic circumferential technology was identified. Plains Midstream Canada and NDT Global formed a close collaboration to assess the severity of circumferential crack features in this line. This paper will discuss integrity aspects from an Operator and Vendor perspective. Challenges identified due to the morphology of the circumferential crack like indications and derived analysis rules and interpretation methodologies to optimize characterization and sizing are presented. Finally, potential opportunities to maintain the integrity of similar assets by applying some of the findings and enhance the management and decision making process are suggested.

The PR China has been very fast developing its energy sector in order to sustain its impressive economic growth. China's installed hydropower capacity is not only the highest in the world; it also shows a globally unique dimension in growth and dynamic. The southwestern province of Yunnan has one of the highest hydropower potentials within China. Its development makes the province one of the key suppliers of electric energy in China, supplying the economic and energy hungry load centers of coastal China but also Southeast Asia. In a decade Yunnan will have an installed hydropower capacity that exceeds that of Canada or the United States. The province is therefore often referred to as China's forthcoming (hydro-) powerhouse or as Asia's battery. Yunnan's rapid development is mainly based on large and prestigious hydropower projects along major rivers, often forming large reservoirs. Secondly it rests on centers of small hydropower development. They are based on small (sub-)catchments where SHP stations mostly form cascades of diversion type projects affecting entire watersheds. Both developments are creating hydroscapes. While Yunnan's large scale hydropower development is relatively well studied, there is an obvious research gap on Yunnan's small hydropower sector. But the latter has not only a huge relevance it also causes serious tangible cumulative implications. This rapid expansion of Yunnan's hydropower sector takes place in one of the most biologically, geographically and ethnically diverse regions in China. This creates a large need for careful management in order to avoid potentially significant environmental and social conflicts. Therefore the article shows the current status of Yunnan's ambitious hydropower development program including its political frame. It critically analyses the environmental and socio-economic consequences of both large and small hydropower projects. It further describes the transboundary implications and the relevance of the power grid.

Southwest China’s Yunnan province is evolving into one of the world’s largest hydro-power-producing regions. It already rivals the world’s largest hydro-producing nations. However, five of Yunnan’s six basins are international and therefore its hydropower development is of great academic and geopolitical interest. While the implementation of large projects on Yunnan’s three large rivers (Jinsha, Mekong and Nu) is relatively well studied, hydropower development outside these three main streams is hardly known. Here, we identified 128 large hydropower projects (≥50 MW) having a capacity of 16.5 GW, along with another 16.4 GW of other types of power generation, neither of which has been discussed in the academic literature yet. The paper utilizes a powershed approach to study the rapid hydropower development underway in Yunnan, both in its implication and challenges (at basin and administrative level) as well as in its trade-offs within the broader electricity context. Yunnan’s power generation and consumption patterns are characterized by diverging interests of local/provincial usage and export utilization. Within the province, the largest (hydro-) power users are energy/electricity intensive industries, which themselves have strong impacts on land use changes. Yunnan is also evolving as a major power exporter, already in 2013 exporting about one-third of its generated electricity mainly to Guangdong’s Pearl River Delta. We see a need for a critical revision of those existing generation and consumption paradigms, which includes a rethinking of major development modes, both in terms of future hydropower generation and utilization projects as well as export obligations.

This paper explains two methods to improve the effectiveness of geoelectrical field measurements. First, we present a method to reduce the number of geoelectrical multielectrode measurements of a survey. The reduction is done by an optimisation of the resulting sensitivity distribution of a superposition of different measurements in comparison with a target sensitivity distribution. The differentiation between important and unnecessary measurements is based on the absolute value of weighting factors. Measurements with small weights are neglected. This procedure can achieve savings up to 70% of all data depending on the task and configuration. We demonstrate the application of data reduction for a synthetic model. In the second part of this paper, we present a method for a fast evaluation and interpretation of field data without a time consuming inversion process. The method is based on weighting coefficients calculated by the object orientated focussing procedure. The filter algorithm provides a fast and easy way to decide whether predefined structures are present along the survey line.

Intelligent inline inspections (ILI) are widely used to guarantee a safe operation of pipelines. The inline inspection provides reliable data in an economic way. Historically, magnetic flux leakage technology (MFL) was one of the main technologies applied in pipeline systems. Within the last few years some minor improvements have been introduced in the existing MFL tool fleets, mainly focusing on a higher resolution. Nevertheless, a general restriction based on the physical basics finally limits the sizing capabilities of corrosion defects, esp. for complex shaped defects. Ultrasonic (UT) is currently the most accurate and reliable In-Line Inspection technology available in the market. These UT ILI Tools record data while travelling through the entire pipeline from Launcher to Receiver. In most cases, the Pipeline Operator does not need to make major adjustments to their pipeline. The latest generation of UT tools offers high inspection velocities — consequently a reduction of medium flow and loss of production can be avoided. In addition, a very high resolution of transducers in axial and circumferential direction provides excellent input for accurate pressure calculations, e.g. based on Riverbottom profiles or even 3D Finite element modeling. Using UT as the inspection method greatly increases the confident level of the inspection survey results. This in turn will give Pipeline Operators a greater peace of mind that their true pipeline condition is known thereby reducing unnecessary and costly digs and repairs. The authors will present some basic background information about ultrasound inspection technologies. State of the art solutions are presented for crack and wall thickness tools. Combining different technologies in one tool offers additional benefit. One single inspection tool with corrosion and crack transducers enables pipeline operators to operate their system safe with a minimized impact. Finally, the authors will present some special solutions for high pressure deep water applications and multi diameter pipeline systems.

The integral reactor is most critical for experimental reaction engineering. However, its design does not come up to current requirements. Based on a tested modular construction principle, new modules for multifunctional integral pilot reactors with a wide range of applications were developed. These modules allow to configure both signle and combination reactors for implementing varied methodical objectives. Two examples illustrate the advantages for the user.

Within the global integrity program of Enbridge a 36/48″ dual diameter pipeline with a total length of approximately1800 km needs to be inspected for wall thickness and axial cracking in a single run. The line consists of 29 sections, each of an approximate length of 60 km. A challenging characteristic of the line is the 36″ launcher and 48″ receiver in 28 of the sections. Thus, the resulting outer diameter change is about 305mm or 33%. From an intelligent inspection perspective additional boundary conditions had to be taken into account, e.g. tight 1.5D bends and a medium with high attenuation — which is especially important for the crack inspection technology. Pipeline operator and in-line inspection (ILI) vendor agreed on an extensive testing and qualification program including small scale tests (200 anomalies) and field verifications. Therefore, the operator witnessed pull tests of the 36/48″ UCM tool at the test facility in Stutensee, Germany during the development phase in 2012. The first inspection in an operating pipeline system, as part of the validation process, was made in July 2012 after only 12 months of development and construction. Some shortcomings of the tool concept were observed within the first inspection, which led to an unsuccessful run. Both parties worked closely together to implement some modifications to the tool. In 2012 and 2013 the modified tool was run a total of 29 times, with further runs planned for 2014. The first excavations have been completed, and show an excellent correlation between tool performance and specification. Further excavations are scheduled for early 2014 that will provide additional feedback to assess and validate the tool. At the time of writing, the 36/48″ tool is fully validated for metal loss defects, and validated for cracks only up to 2.5mm in depth. The authors will present in detail the development of the tool and the definition of the validation process. Mechanical and operational conditions are discussed. The predefined validation process of the tool is briefly presented and the test results are discussed in detail. Furthermore, field verification results are presented.

Objectives: The practice of homeopathy rests on symptoms, which have been produced by medicinal substances in healthy volunteers, often applied at ultramolecular dilutions. It is unknown whether these symptom patterns are due to specific effects or chance fluctuation. Methods: We tested the hypothesis that a homeopathic substance can bring about symptoms different from observation and placebo in a double-blind, placebo-controlled crossover design with baseline observation. Results: 87 out of 118 healthy volunteers took both placebo and homeopathic belladonna 30CH in random sequence, after a 2-week observation period, and finished the 8-week trial. Apart from an insignificant tendency for subjects to report more symptoms with belladonna (mean number: 27.34), as compared to observation (24.26) or placebo (24.17), there was no indication that subjects reacted differently to homeopathy than to placebo or during baseline. Conclusion: There is no indication that belladonna 30CH produces symptoms different from placebo or from no intervention. Symptoms of a homeopathic pathogenetic trial (HPT) are most likely chance fluctuations.

Summary The concept of periodontal treatment has radically changed over the past decades from a very aggressive surgical approach of pocket elimination to a conservative treatment. The treatment objective today is just removing the periodontal disease causing agents. Regarding this aspect the use of lasers in periodontal treatment may be the next step towards a more conservative treatment. Selective ablation of calculus requires preferential absorption by the material to be removed compared to the healthy tissues. In Periodontology the use of the Nd:YAG laser is restricted to the field of soft tissue management, no ablation of calculus is possible. Using conventional CO2 lasers runs the risk of thermal overheating of the pulp. Moreover due to the absorption characteristics uncontrolled destruction of gingival tissue as well as cementum and enamel occurs. Excimer and Er:YAG lasers can be used to remove calculus but uncontrolled ablation of healthy tooth structure takes place. The frequency doubled Alexandrite (377 nm) laser allows a selective ablation of calculus based on natural differences in absorption. Calculus and microbial plaque are removed quickly and easily while cementum and other healthy tooth structures remain unchanged. In order to establish clinically healthy gingiva and to prevent further loss of attachment the use of the frequency doubled Alexandrite laser seems to be a very promising step for the future of periodontal therapy. Moreover the expectation of a sound maintenance therapy will be fulfilled by using this laser.

Inline inspection (ILI) identifies most significant anomalies - at the time of inspection. To recognize those individual features, which have the highest potential to enter these ranks, perhaps soon, is a challenging question, which is not necessarily covered with established ILI approaches. Whether the circumstances permit the identification and reliable description of individual corrosion hot spots depend on the ILI quality, the specific feature shape-dependent sizing, the comparability of the data and the time-dependent development of the anomaly. This case study demonstrates the enormous benefits of the combination of two technologies. The robust, indirect Magnetic Flux Leakage (MFL) methodology and the direct Ultrasonic Testing (UT) ILI tool. The intelligent interpretative combination of the two ILI information sources exceeds significantly the straight forward statistical combination benefit. The presented approach demonstrates how to: • identify features not suitable to UT stand alone sizing. • compensate systematic errors from MFL sizing models and calibration assumptions. • introduce UT shape information as major improvement to MFL sizing. • apply MFL amplitude based depth sizing. • reduce the subsequent sizing tolerance to values, which allow corrosion prediction based on even short term repeated ILI intervals. Applied to the identified group of pinholes and embedded pinholes with an average maximum depth of more than 50% the method delivered a depth sizing accuracy of ±6.0% wall thickness at 80% certainty. The fact, that even smaller corrosion growth rate values become resolvable, allows for the equivalent shortening of the re-inspection intervals and for the prolongation of the validity of prediction, whatever may be advisable in specific cases. Also it is shown, that this approach does not require to rerun similar tools, because systematic errors can be compensated absolutely with this approach. The optimization of inspection strategies and methods with regard to specific pipeline problems can have monetary benefit even at higher inspection costs. More sophisticated ILI systems requiring specialist data analysis become justified for equivalent pipeline use cases. The presented combination of the two independent ILI methodologies bears significant useful potential to approach aggressive corrosion mechanisms, e.g. microbial corrosion or CP shielding.

To sustain their impressive economic growth and to provide electricity for the two most populated states, PR China and India are aggressively developing their energy sector. Regenerative energy, mainly hydropower, plays a key role in their present and future energy sector strategy. The speed of hydropower development shows a dimension which is unique worldwide. This extreme rapid development is mainly based on controversial large dams, but also on the fast development of small scaled hydropower projects.

Ultrasonic crack detection represents a reliable and accepted inline inspection technology for the application in liquid media. The technology is long standing and considered as industry standard [1–3]. As a result of various demands, e.g. increased temperature levels above 70°C, high pressures exceeding 100 bars and medium types (e.g. heavy crude oil) with inherently high damping and temperature dependency of the damping characteristic the complexity can be primarily found within the bounding conditions. The reduction of inner pipeline diameter, e.g. below 120 mm, represents a further increase of degree of complexity. This paper gives access to the design and development approach chosen by ROSEN for ultrasonic crack detection tools and the case of pipelines with an outer diameter ranging from 6″ to 8″ . All previously mentioned issues and requirements are considered. The mechanical design of the ultrasonic crack detection tools is described.Copyright © 2010 by ASME

Utilizing Fourier Transform Infrared Spectroscopy (FTIR) in specular reflectance mode chemical changes of root cement surfaces due to laser radiation were investigated. A total of 18 samples of root cement were analyzed, six served as controls. In this study laser energies were set to those known for removal of calculus or for disinfection of periodontal pockets. Major changes in organic as well as inorganic components of the cementum were observed following Nd:YAG laser irradiation (wavelength 1064 nm, pulse duration 250 μs, free running, pulse repetition rate 20 Hz, fiber diameter 320 μm, contact mode; Iskra Twinlight, Fontona, Slovenia). Er:YAG laser irradiation (wavelength 2.94 μm, pulse duration 250 μs, free running, pulse repetition rate 6 Hz, focus diameter 620 μm, air water cooling 30 ml/min; Iskra Twinlight, Fontona, Slovenia) significantly reduced the Amid bands due to changes in the organic components. After irradiation with a frequency doubled Alexandrite laser (wavelength 377 nm, pulse duration 200 ns, q-switched, pulse repetition rate 20 Hz, beam diameter 800 μm, contact mode, water cooling 30 ml/min; laboratory prototype) only minimal reductions in the peak intensity of the Amide-II band were detected.

Aim of the study was to investigate the impact of a new picosecond laser emitting blue light on tooth surfaces in order to remove calculus. The radiation may be comfortably transmitted via 25 micrometers diameter fiber optics. The resulting fluence at the tooth was found to be to low for ablation of calculus via nonlinear effects. Higher absorption of the 446 nm radiation by calculus compared to heathy tissues can provide preferential heating and evaporation of the calculus. The surface of thick calculus is irregular rough thus comprising a large interface to the surrounding cooling medium contra acting the preferential heating. In summary the study indicates the possibility flat layers of calculus by thermal effects. Carbonization in healthy tissues is the major problem concerning removal of subgingival calculus with thermal effects.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The therapy of initial carious lesions aims in a minimal invasive removal of infected dental hard tissues. Typically standardpreparation instruments bear the risk of removing a big amount of sound structures as a result of access. On the other handthe competence ofEr:YAG lasers for caries removal has been repeatedly proven.Aim of this study was to compare cavity preparations at simulated clinical conditions performed by two different Er:YAGlaser systems, one working in noncontact mode (KaVo Key Laser; Biberach, Germany) the other working in contact mode(Continuum Biomedical DELight Er:YAG Laser System, Santa Clara, CA).The sample material consisted of 15 randomized selected extracted human molars clinically presenting initial canons lesionslocated in the occlusal fissure area. In the first part of the study each lesion passed standard clinical examinations. Visual

While earlier periodontal investigations have proved the frequency doubled Alexandrite laser to eliminate efficiently and selectively dental calculus as well as bacteria the aim of this study was to demonstrate the safety of this laser for removal of dental calculus with respect to the dental pulp. Four adult Labrador dogs were treated with a frequency doubled Alexandrite laser (laboratory prototype, q-switched, fiber guided, wavelength 377 nm, pulse duration 1 microsecond, pulse repetition rate 70 Hz, water cooling) to remove dental calculus. After performing a modified Widman flap procedure the buccal surface of nine teeth in the lower and upper right jaw were irradiated for four minutes per tooth. Three different laser fluences up to four times higher than the fluence required for calculus removal were used (1.5, 3 and 6 J/cm2). At three other sites of the right jaw deep cavities were prepared with a dental drill and filled with compomere material (DyractR, Dentsply, Germany) to serve as a positive control with regard to possible pulpal reactions. The corresponding teeth of the lower and upper left jaw served as controls. Animals were sacrificed one day, one week, four weeks and six weeks after treatment. Teeth were separated, fixed in formalin and decalcified. After embedding and sectioning the histological sections were stained and investigated by a totally blinded investigator (P.A.R). Histological investigations revealed that irradiation with the frequency doubled Alexandrite laser for periodontal treatment with fluences of 1.5 J/cm2 -- those fluences necessary for the selective removal of dental calculus and microbial plaque -- had no adverse side effects to the pulpal tissues. Moreover this pulpal safety study demonstrated that even applying fluences two or four times higher than those suggested for calculus removal do not lead to observable changes or alterations in the odontoblast cell layer or the pulpal tissues. No inflammatory reactions and no differences between irradiated and control teeth occurred, while the positive controls showed reactions in the odontoblast cell layer and the connective pulpal tissue.

Periodontal therapy aims in a most sufficient cleaning of tooth surfaces from supra- and subgingival calculus. As a standard dental procedure teeth are treated with ultrasonic devices. The competence of the frequency doubled Alexandrite laser for a highly effective and selective removal of calculus has been repeatedly proved. Aim of the study presented here was to determine the efficiency at simulated clinical conditions of the frequency doubled Alexandrite laser (laboratory prototype, q-switched, fiber guided, wavelength 377 nm, pulse duration 1 microsecond, pulse repetition rate 70 Hz, water cooling) by quantifying it's calculus removing efficiency. The evaluated data were compared to those obtained with an ultrasonic calculus remover. In the first part of the study sample material consisted of 23 pigs' jaws. They were divided into two groups. The teeth of one group were cleaned on their buccal surfaces using an ultrasonic device (Sonosoft Lux, KaVo, Biberach, Germany; tip #9). Than hand-guided cleaning was performed until no further improvement in cleanness was visible. Cleaning time was measured. Photographic documentation was taken before and after the treatment. The teeth in the second group were cleaned engaging a frequency doubled Alexandrite laser. Treatment time was measured and photographs were taken in the same way. In the second part of the study 21 surfaces of human teeth set up in an artificial pocket model were treated with both systems again. Measurements followed the same protocol. The results strongly support the use of the frequency doubled Alexandrite laser for calculus removal.

Er: YAG lasers as well as the frequency doubled Alexandrite laser have been suggested for the use in periodontal therapy and so for the elimination of calculus and the treatment of infected root cement. Intended is the laser application inside the gingival pocket. In consequence, both these lasers may be used in areas close to cervical or approximal location, or even on the fillings' surfaces. Light cured composite and compomer materials are in use for these types of fillings among others. Aim of the study presented here was to compare the effect of an Er: YAG laser (wavelength 2.94 μm, pulse duration 250 μs, free running, fluence 4.5 J/cm 2 and 21.4 J/cm 2 ) on compomers and composites with the results following irradiation with a frequency doubled Alexandrite laser (wavelength 377 nm, pulse duration 200 ns, fluence 3 Jcm -2 and 6 J/cm 2 ). The surface of standardized compomer and composite samples were irradiated with both laser wavelengths (either frequency doubled Alexandrite or Er: YAG laser) using the same standardized application protocol. Scanning electron microscopic investigation showed that irradiation with both lasers causes surface changes in composites and compomers removing calculus with these lasers.

Periimplantitis is one of the major factors for the loss of dental implants. Due to the minor defense ability of the tissue surrounding the implant compared to natural teeth treatment of periimplantitis in the early stage is very important. Reducing bacteria with a laser might be the most successful step in therapy of periimplantitis. Aim of the study was to observe changes in surface morphology of seven different implants after irradiation with three different lasers. Two kinds of flat round samples were prepared by the manufacturers either identical to the body surface or to the cervical area of the corresponding implants. The samples were irradiated using different power settings. The lasers used were a CO 2 laser (Uni Laser 450P, ASAH Medico, Denmark; fiber guided, wavelength 10.6 μm, max. average power 8.3 W, soft-pulse and cw) an Er: YAG laser (KaVo Key Laser II, wavelength 2.94 μm, pulse duration 250 - 500 μs, pulse energy 60 - 500 mJ, pulse repetition rate 1 - 15 Hz, focus diameter 620 μm, air-water cooling; Biberach, Germany) and a frequency doubled Alexandrite laser (laboratory prototype, q-switched, fiber guided, wavelength 377 nm, pulse duration 1 μs, pulse repetition rate 30 Hz, water cooling). After irradiation the implant surfaces were investigated with a Scanning Electron Microscope. Ablation thresholds were determined. After CO 2 laser irradiation no changes in surface morphology were observed whereas using the pulsed Er: YAG or frequency doubled Alexandrite laser even at low energies loss of integrity or melting of the surface was observed. The changes in surface morphology seem to depend very strongly on the type of surface coating.

Aim of this presentation is to review the role of the Er:YAG laser in dentistry and to give a general overview on the work done with it up to date. A look at the development and evolution of this system is given as well as a brief introduction into the basic principles of ablation at the characteristic wavelength 2.94 micrometer. The more important research reports of the different groups all over the world are summarized and the large field of applications such as cavity preparation, caries ablation, periodontology and bacterial reduction is considered.

With respect to lasers emitting within the mid infrared spectral domain fiber applicators are being developed. Intented is the use of these lasers in periodontal therapy and their application inside the gingival pocket. Aim of the study presented here is to compare the effect of an Er:YAG laser (wavelength 2.94 μm, pulse duration 250 μs, free running, different power settings) on dental calculus with the results following irradiation with a frequency doubled Alexandrite laser (wavelength 377 nm, pulse duration 100 ns, q-switched, fluence 1 Jcm -2 ). The surface of freshly extracted wisdom teeth and of extracted teeth suffering from severe periodontitis were irradiated with both laser wavelengths (either frequency doubled Alexandrite or Er:YAG laser) using a standardized application protocol. Calculus on the enamel surface, at the enamel cementum junction and on the root surface was irradiated. For light microscope investigations undecalcified histological sections were prepared after treatment. For the Scanning Electron Microscope teeth were dried in alcohol and sputtered with gold. Investigations revealed that with both laser systems calculus can be removed. Using the frequency doubled Alexandrite laser selective removal of calculus is possible while engaging the Er:YAG laser even at lowest energies necessary for calculus removal healthy cementum is ablated without control.

The basic laser ablation processes of dental hard tissue will be reviewed. Pulse lengths covered in this presentation range from some femto seconds to the cw-mode, wavelengths from the ultraviolet to the infrared spectral domain. The underlying tissue removal mechanisms extend from surface evaporation, to photochemical processes, to mediated explosive ablation, to plasma processes. The most effective mechanism is the explosive process. Highly controlled tissue removal at low ablation rate can be obtained using plasma mediated ablation. Good tissue specivity characterizes the ablation in the near UV region of the spectrum.

During prior studies it could be demonstrated that engaging a frequency double Alexandrite-laser allows a fast and strictly selective ablation of supra- and subgingival calculus. Furthermore, the removal of unstained microbial plaque was observed. First conclusions were drawn following light microscopic investigations on undecalcified sections of irradiated teeth. In the present study the cementum surface after irradiation with a frequency doubled Alexandrite-laser was observed by means of a scanning electron microscope. After irradiation sections of teeth were dried in alcohol and sputtered with gold. In comparison irradiated cementum surfaces of unerupted operatively removed wisdom teeth and tooth surfaces after the selective removal of calculus were investigated. A complete removal of calculus was observed as well as a remaining smooth surface of irradiated cementum.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

During prior studies it could be demonstrated while engaging a frequency doubled Alexandrite-laser (wavelength 380 nm, pulse duration 100 ns, fluence 1 J/cm2, pulse repetition rate 110 Hz) a fast and strictly selective ablation of supra- and subgingival calculus is possible. Even the removal of unstained microbial plaque was observed. First conclusions were drawn after light microscopical investigations on undecalcified sections of irradiated teeth. In the present study the cementum surface after irradiation with a frequency doubled Alexandrite-laser was observed by means of a Scanning Electron Microscope. After irradiation sections of teeth were dried in alcohol and sputtered with gold. In comparison irradiated cementum surfaces of unerupted operatively removed wisdom teeth and tooth surfaces after the selective removal of calculus were investigated. A complete removal of calculus was observed as well as a remaining smooth surface of irradiated cementum.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The aim of the study was the selective removal of dental calculus by means of pulsed lasers. In a first approach the optical characteristics of subgingival calculus were calculated using fluorescence emission spectroscopy (excitation laser: N2-laser, wavelength 337 nm, pulse duration 4 ns). Subgingival calculus seems to absorb highly in the ultraviolet spectral region up to 420 nm. According to these measurements a frequency doubled Alexandrite-laser (wavelength 377 nm, pulse duration 100 ns, repetition rate 110 Hz) was used to irradiate calculus located on enamel, at the cementum enamel junction and on the root surface (located on dentin or on cementum). Irradiation was performed perpendicular to the root surface with a laser fluence of 1 Jcm-2. During the irradiation procedure an effective water cooling-system was engaged. Histological investigations were done on undecalcified sections. As a result, engaging low fluences allows a fast and strictly selective removal of subgingival calculus. Even more the investigations revealed that supragingival calculus can be removed in a strictly selective manner engaging a frequency doubled Alexandrite-laser. No adverse side effects to the surrounding tissues could be found.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Selective ablation is fixed to a range of fluences predicted by the ablation thresholds of infected and healthy tooth structures respectively. The aim of the study was to develop a dental handpiece, which guarantees homogeneous fluence at the irradiated tooth surface. Furthermore the point of treatment should be cooled down without energy losses due to the cooling system. We suggest the direct coupling of the laser radiation into a laminar stream of liquid, which may act in turn as a lengthened beam guide. The impacts of the laser radiation and of the cooling medium hit exactly the same point. Hot ablation debris is removed out of the crater by the flush of the water jet. While the surface of a bare fiber working on contact mode is destroyed after a few shots, it was shown that coupling the laser radiation into a stream of liquid prevents this destruction. Putting together the benefits of this special handpiece short overall treatment times seem to be possible. High average power can be applied to the tooth without the threat of thermal damage. Furthermore no time consuming cutting of the fiber prolongs the treatment time.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Caries selective ablation is fixed to a window of fluences predicted by the ablation thresholds of carious and healthy dentin, respectively. The aim of the study was to develop a dental handpiece which guarantees homogeneous fluence at the irradiated tooth surface. Furthermore the point of treatment should be cooled down without energy losses due to the cooling system. We suggest the direct coupling of the laser radiation into a laminar stream of liquid, which acts in turn as a lengthened beam guide. The impacts of the laser radiation and of the cooling medium fall exactly into the same point. Hot ablation debris is removed out of the crater by the flush of the water jet. Fluences are constant if the handpiece is used in contact mode or at a distance. Normally the surface of a bare fiber working in contact mode is destroyed after a few shots. Coupling the laser radiation into a stream of liquid prevents this destruction. Putting together the benefits of this special handpiece short overall treatment times seem to be possible. High average power can be applied to the tooth without the threat of thermal damage. Furthermore no time consuming cutting of the fiber prolongs the treatment time.

In a preceding trial the absorption characteristics of subgingival calculus were calculated using fluorescence emission spectroscopy (excitation laser: N2-laser, wavelength 337 nm, pulse duration 4 ns). Subgingival calculus seems to contain chromophores absorbing in the ultraviolet spectral region up to 420 nm. The aim of the actual study was the ablation of sub- and supragingival calculus using a frequency doubled Alexandrite-laser (wavelength 377 nm, pulse duration 100 ns, repetition rate 110 Hz). Extracted human teeth presenting sub- and supragingival calculus were irradiated perpendicular to their axis with a laser fluence of 1 Jcm-2. Using a standard application protocol calculus was irradiated at the enamel surface, at the junction between enamel and root, and at the root surface (located on dentin or on cementum). During the irradiation procedure an effective water cooling-system was engaged. For light microscopical investigations undecalcified histological sections were prepared after treatment. The histological sections revealed that a selective and total removal of calculus is possible at all locations without ablation of healthy enamel, dentin or cementum. Even low fluences provide us with a high effectiveness for the ablation of calculus. Thus, based on different absorption characteristics and ablation thresholds, engaging a frequency doubled Alexandrite-laser a fast and, even more, a selective ablation of sub- and supragingival calculus is possible without adverse side effects to the surrounding tissues. Even more, microbial dental plaque can be perfectly removed.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Ablation thresholds of healthy dentin were measured engaging four different pulsed laser systems, emitting in the near ultraviolet (wavelength 355 nm, wavelength 377 nm), in the near infrared (wavelength 755 nm), and in the mid infrared (wavelength 2.9 micrometers ) spectral region. A pulse duration of 200 ns was used during experiments with the Alexandrite-laser (wavelengths 377 nm and 755 nm) whereas at the wavelength 355 nm pulse duration was fixed at 9 ns and at wavelength 2.9 micrometers pulse duration was set to 200 ns again. Two well defined ablation thresholds could be detected using laser wavelengths which are well absorbed by the target (near UV, mid infrared). Due to low absorption of near infrared wavelengths in healthy dentin, high fluences must be engaged for ablation of healthy dentin. In this spectral region only a more or less statistically appearing ablation threshold was observed. Caused by high fluences unpredictable plasma formation takes place. Even so, short pulse duration leads to high peak power, thus originating plasma.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The aim of the study was to describe the effects of a caries selective laser system applied on human dentin. Ablation efficiencies of laser pulses emitted from a frequency doubled, gain-switched Alexandrite-laser (wavelength 377 nm) were determined for carious as well as for healthy dentin. Laser pulsed of different pulse duration, 100 ns and 1.6 microsecond(s) , were investigated in comparison. In spite of the different peak power- due to the different pulse durations-the ablation thresholds and ablation efficiencies were found to be about the same for 100 ns as for 1.6 microsecond(s) laser pulses. In healthy dentin two ablation efficiencies (0.03 and 0.12 mm3J-1), according to the two different ablation regimes, could be described. An overall ablation efficiency of carious lesions from 34 different teeth was determined to be about 0.3 mm3J-1. Fluences used for morphological and histological assessment were chosen with respect to the previously described ablation thresholds of healthy dentin. With respect to operating speed, the '99% selectivity mode' for fast caries ablation with fluences within the first ablation regime of healthy dentin (2.6 +/- 0.3 Jcm-2) were used. The effects of different surrounding media-water and air-were studied in comparison. Light- and scanning electron microscopic investigations were performed. If during irradiation the tooth was submerged in water, craters in healthy dentin were small and uncolored. Crater walls demonstrated only a few microns of surface roughness. Ablation debris remains associated to the crater wall. Irradiation in air results in an early carbonization accompanied with melting and cracking of the irradiated dentin. As long as water cooling is provided the histological findings reveal that engaging a frequency-doubled Alexandrite-laser caries selective ablation is possible without too much damage to the surrounding healthy tissues. Nevertheless an active flow of cooling water is desirable in order to remove hot ablation debris out of the crater.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Engaging four different pulsed laser systems emitting in the near ultraviolet (wavelength 355 nm, wavelength 377 nm), in the near infrared (wavelength 755 nm), and in the mid infrared (wavelength 2.9 micrometers ) spectral region ablation thresholds of healthy dentin were determined. During experiments with an Alexandrite-laser (wavelengths 377 nm and 755 nm) a pulse duration of 200 ns was used, whereas at wavelength 355 nm pulse duration was fixed at 9 ns and at wavelength 2.9 micrometers pulse duration was set to 200 ns again. Using laser wavelengths which are well absorbed by the target (near UV, mid infrared) two well defined ablation thresholds could be detected. Due to low absorption of near infrared wavelengths in healthy dentin, high fluences must be engaged for ablation of healthy dentin. In this spectral region only a more or less statistically appearing ablation threshold can be observed. Caused by high fluences unpredictable plasma formation takes place. Even so, short pulse duration leads to high peak power, thus originating plasma.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The aim of the study was to describe the effects of different surrounding media -- water and air -- during application of a caries selective laser system on healthy dentin, the substance which should be preserved. Fluences used in this study were chosen with respect to the previously described ablation thresholds of healthy dentin. Fiber optics (0 400 micrometers , N.A. 0, 12) were used for transmission of the laser radiation. Luminescence emission was recorded time resolved in order to differentiate between fluorescence and plasma emission. Hot plasma seems to be rigorously reduced if the irradiation is performed under water. Scanning electron microscopical investigations were performed. Craters irradiated in air show cracks and signs of melting whereas crater walls after irradiation under water demonstrated rough surfaces and open dentinal tubules. Cracks did not occur if irradiation was performed in water. As long as water cooling is provided a Q-switched, frequency-doubled Alexandrite-laser providing fluences of 5 Jcm-2 at the tooth surface does not produce hot plasma during the ablation of healthy dentin.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Preparing teeth the operating speed of laser systems is limited by the temperature increase at the pulp. In dentin the absorbed energy generated by a caries selective laser system working in the subthreshold fluence range for healthy dentin is converted nearly by 100% into heat. This heat is partly transferred to the pulp and endangers the vitality of the pulp. The aim of our measurements was to determine the temperature increase in the pulp chamber as a function of dentin thickness between the lasering point and the pulp chamber. The caries selective conditions were produced by a frequency doubled Alexandrite-laser (wavelength 377 nm, fluence 2 Jcm-2). Freshly extracted, sound human teeth were cut into slices ranging from 0.1 mm to 2 mm in thickness. A miniature bead thermistor measured the temperature on the pulpal side of the tooth slice in corresponding position to the irradiating fiber. Reducing the thickness of the remaining dentin results in an exponential increase of temperature. We examined the influence of fluence and pulse repetition rate on the temperature in the pulp chamber.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The aim of the study was to determine changes in dental hard tissues afler caries selective laser impact. Light and scanning electron microscopic investigations were perfonned. The effects of a frequency-doubled, q-switchcd Alexandrite- laser (wavelength 377 urn, pulse duration 100 ns, various repetition rates) on healthy and carious dentin were Studied. Fluences used in this study were chosen with respect to the previously discribed ablation thresholds of healthy dentin. With respect to operating speed, the "99 % selectivity mode" for fast caries ablation was used on carious as well as on healthy dentin. So, from the clinical and especially histological point ofview, fluences in the region ofthe second ablation thresholdof healthy dentin (3 J/cm2) were most interesting. Furthermore laser impacts with fluences up to 7 J/cm2 were studied. Fibreoptics ranging in diameter from 300 to 400 un were engaged. Because there is neglegtible absorption oflaser energy in waterin this spectral region all laser applications could be done under water.Histological examinations of craters in hard tissues were performed without decalcification of samples. Craters in dentalhard tissues were sharply cut and followed closely the profile of the illuminating fibre. Crater walls demonstrated only a fewmicrons of surface roughness. Apart from a very tiny zone due to temperature rise, surrounding hard tissues seem to be totallyuneffected, anytime, cracks did not occure.

The aim of the study was to describe the appropriate fluence necessary for the effective removal of dentil decay byablation processes without or with at least minimal removal of healthy dentin. The experiments were conducted at twowavelengths [355 rim (frequency tripled, Q-switched Nd:YAG-laser) and 377 nm (frequency doubled, gain-switched Alexandrite-laser)] found to be close to the maximum ofpreferential absorption of carious denin over healthy dentin. Optoacoustic techniques were applied to determine the ablation thresholds of healthy and carious dentin. The ablationefficiencies at characteristic fluences were determined using non-tactile microtopography. IDuring all experiments a fibre optic delivery system was engaged. Strictly selective ablation of carious dentin occured for fluences exceeding 0.4 Jcm2 up to 1.2 Jcm2 at 355nmor 0.5 Jcnr2up to 1.8 Jcnr2 at 377 nm respectively. In contrast relative selective ablation occured for higher fluences.A second ablation threshold characterized by a dramatical increase of ablation efficiency was found in carious as well as

The aim of this study was to compare the conditions for selective removal of carious lesions by pulsed lasers emitting wavelengths in the near UV in contrast to lasers emitting in the IR spectral region at 2.9 micrometers . Absorption measurements of carious lesions and healthy dentin revealed highest absorption differences at wavelengths between 320 and 520 nm. The effects of a frequency doubled, gain-switched Alexandrite-laser (wavelength 377 nm) and a q- switched Er:YAG-laser (wavelength 2.9 micrometers ) on carious and healthy dentin were studied in comparison. Both lasers emitted pulses of 200 ns duration. The ablation thresholds for the different tooth structures were determined. The ablation threshold of carious lesions is about the same for the Er:YAG as for the second harmonic Alexandrite-laser. For the Er:YAG-laser the ablation threshold of healthy dentin is about 2 times higher than the ablation threshold of carious lesions. In the case of the second harmonic Alexandrite-laser the difference between ablation is 4 times higher. Thus, regarding the window of fluences sufficient for truly caries selective ablation, the conditions for selective removal of carious dentin are better in the near UV than in the IR spectral region at 2.9 micrometers .

The aim of the study was to find conditions for selective ablation of carious dentine. Absorption characteristics of healthy enamel, dentine, and carious lesions were studied by means of microspectrophotometry. It was found that in the spectral range of 330 to 520 nm optical density of carious dentine is higher by about a factor of 4 as in respect to healthy dentine. In the second part of the study, ablation thresholds were studied for different tissues at 355 nm (frequency tripled Q-switched Nd:YAG-Laser). By means of a piezoelectric detector, ultrasonic waves generated by ablation and subthreshold thermoelastic mechanisms were detected. Employing a fiber-optic delivery system, selective ablation of carious dentine occurred for pulse energies exceeding 0.4 Jcm-2 up to 1.2 Jcm-2.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.