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Tobacco use is a major public health issue that has its onset primarily during the pediatric years. Preventing the onset of tobacco use by children and adolescents should be a priority. A comprehensive strategy includes interventions by pediatricians and other health professionals, policy changes, advertising restrictions, comprehensive school health education programs, and community advocacy. Because the physician–parent–child relationship is unique, physicians have many opportunities to help prevent tobacco use, both in their offices and in their communities.

The World Health Organization’s (WHO) constitution states that enjoyment of the ‘‘highest attainable standard of health is one of the fundamental rights of every human being...’’. There is ample evidence that not everyone enjoys the highest standards and that there are inequities in health worldwide. Income, gender, race, ethnicity, and social status may affect whether an individual is born and grows up healthy, or has access to good health care [1]. Whether described in terms of health equity, healthcare inequality, health disparities, or social justice, we know that, in the simplest and most stark terms, vast numbers of children, women, and men across the globe do not enjoy the basic human right of good health care. There have been considerable scientific, medical, and policy analyses of the causes of these inequities and their potential solutions. Because, however, many of these causes, and solutions, are society-wide issues, e.g., poverty and its reduction, healthcare system barriers and reforms, expansion of health literacy, etc., there is a great need for both political will and solutions which are concrete, manageable, and, above all, can lead to measurable success in removing barriers to good health across populations. Tobacco control as a potential solution

The main spectroscopic methods used to determine the specific figures of merit for stationary 3 μm Er laser generation are discussed. The detrimental effect of the concentration quenching of the 4 I 9/2 Er level is expressed by a new figure of merit.

Luminescence and lifetime measurements are presented for LaSr2Ga11O20 : Cr3+. The room-temperature emission is dominated by a broadband stretching from ≈ 670 nm to beyond 1.1 μm. It is suggested that the Cr3+ ions substitute in two distinct high-field sites with predominantly octahedral coordination.

Emission and excitation spectra of a Ni-doped forsterite crystal have been measured at temperatures down to 15 K. Three emission bands are evident, the most intense having a zero-phonon line at 1374 nm (7280 cm-1) and a lifetime of 1.2 (±0.1) ms at 20 K. Evidence suggests that Ni2+ substitutes in the centrosymmetric M1 site.

New experimental results concerning the concentration quenching of the luminescence of the 4I 9 2 level of Er3+ in different laser crystals, at room temperature, are presented. The detrimental effect of the concentration quenching of 4I 9 2 level on the 3 μm emission of Er lasers, expressed by the figure of merit, h, is discussed.

Laser safety standards are detailed technical documents arising from the complexity of the different mechanisms, depending on the parameters of the laser beam, by which lasers interact with living tissue. As a result, their interpretation by non-expert laser users, who are concerned about safety issues, can cause many difficulties. Based on experience in advising industrial and medical laser users, we have developed a primer which (i) provides step-by-step guidance in the interpretation and use of the laser safety standards, and (ii) explains how to calculate the laser irradiance (on the retina or the skin) to which the user may be subjected in typical situations. A computer program has also been developed which, through a series of questions and answers, guides the user through the calculation of the maximum permissible exposure level and the nominal optical hazard distance for the application of interest. The overall package should be particularly useful to laser safety officers and users of lasers for research applications, as an independent check on safety calculations. It also provides a useful complement to the many worked examples in the laser safety standards.

Luminescence spectra of an iron-doped (0.2%) synthetic crystal of forsterite have been measured at low temperature (15 K). These show several zero-phonon lines at 813, 1025, 1093 and 1134 nm, all with phonon side bands. The emission at 1093 nm is due to chromium (Cr 4+ ) and occurs also in both nominally pure crystals and chromium-doped samples. However, the 813 nm line is ascribed to Fe 3+ ions, probably in tetrahedral (Si) sites, on the basis of the measured lifetime (15.5 ± 0.5 ms) and the analysis of excitation spectra. The 1025 and 1134 nm lines have measured lifetimes of 8.4 and 5.7(±0.5) μs respectively at 20 K and are similar in other respects. It is suggested that these lines may be due to Fe 2+ ions in octahedral (Mg) sites.

A comparative characterization study of diamond and diamond-like carbon (DLC) films deposited using plasma-enhanced chemical vapour deposition is presented. The films were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and Raman spectroscopy. As a result of these studies structural and chemical information was obtained on the carbon films. The SEM examination indicated the presence of high levels of stress in the diamond films. The ability of XPS and Raman spectroscopy to distinguish between diamond-type carbon (sp 3 hybridized) and graphitic carbon (sp 2 hybridized) is demonstrated.

Like other chronic conditions, nicotine dependence offers both challenges and rewards to clinicians. The treatment of this condition frequently requires experience in pharmacology, behavioral science, and social aspects of medicine. Physicians are uniquely qualified to assist patients in their efforts to overcome the multifaceted condition of tobacco addiction. In providing this treatment, the clinical challenges are far outweighed by the benefit to patients who stop smoking. For many patients, smoking cessation is, by far, the most important step they can take to improve their health and increase their life span. Physicians who help patients accomplish this difficult goal provide a life-saving service. There is sufficient scientific evidence to guide physicians in their approach to smoking patients. Brief, systematic interventions have been shown to increase patient smoking cessation rates. The intervention can be described in four steps: ask about smoking, advise smokers to stop, assist those who want to stop, and arrange adequate follow-up. These interventions are used consistently when a smoking cessation program is adopted by an entire office practice. The components of this office-based program include defining staff roles, maintaining a smoke-free office, stocking appropriate materials, making use of the medical record to identify smokers and to remind staff to intervene, and monitoring patient progress. The potential public health impact of physician intervention with smoking patients is enormous. Even with very modest expectations of cessation rates, 100,000 physicians using effective intervention can produce over 3 million new ex-smokers in the United States each year. In conjunction with other community-based tobacco control efforts, this physician-lead effort will result in a marked reduction in the morbidity and mortality caused by smoking and, thus, control of "the most important public health issue of our time."

Optical and magnetic-circular-dichroism--optically-detected-magnetic-resonance studies have been carried out on Co-doped ${\mathrm{LiGa}}_{5}$${\mathrm{O}}_{8}$. The Co ions are found to be predominantly in the 2+ charge state and to substitute for tetrahedrally coordinated ${\mathrm{Ga}}^{3+}$ in the ${\mathrm{LiGa}}_{5}$${\mathrm{O}}_{8}$ lattice, in sites which are shown to have ${\mathit{C}}_{3}$ point-group symmetry. The strong absorption bands from the ground state $^{4}$${\mathit{A}}_{2}$${(}^{4}$F) to the excited states $^{4}$${\mathit{T}}_{1}$${(}^{4}$P) and $^{4}$${\mathit{T}}_{1}$${(}^{4}$F) are each split by the low-symmetry ${\mathit{C}}_{3}$ field. A combination of the low-symmetry field and spin-orbit coupling is responsible for the ground-state splitting of 19.5\ifmmode\pm\else\textpm\fi{}0.5 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ observed by fluorescence line narrowing. Strong broadband luminescence is observed from the $^{4}$${\mathit{T}}_{1}$${(}^{4}$P) level to three lower levels, $^{4}$${\mathit{A}}_{2}$${(}^{4}$F), $^{4}$${\mathit{T}}_{2}$${(}^{4}$F), and $^{4}$${\mathit{T}}_{1}$${(}^{4}$F), with a lifetime that is constant at 200 ns from 10 K up to room temperature. The optically-detected magnetic-resonance studies show that the ${\mathrm{Co}}^{2+}$ ions are in sites which have axial symmetry along 〈111〉-type axes of the unit cell, indicative of the ${\mathit{C}}_{3}$ symmetry present in these substitutional sites. We give a detailed crystal-field model for the ${\mathrm{Co}}^{2+}$ ion in the ${\mathit{C}}_{3}$ site in ${\mathrm{LiGa}}_{5}$${\mathrm{O}}_{8}$ and deduce the crystal-field parameters from our experimental data.

Effective tobacco control efforts have resulted in substantial declines in tobacco use and tobacco-related cancer deaths in the United States. Nearly 40% of reductions in male lung cancer deaths between 1991 and 2003 can be attributed to smoking declines in the last half century. Nevertheless, tobacco use still remains the single, largest preventable cause of disease and premature death in the United States. Each year, smoking and exposure to secondhand smoke result in nearly half a million premature deaths of which nearly one-third are due to cancer. In a previous report, we described youth and adult smoking prevalence and patterns and discussed policy measures that had proven effective in comprehensive tobacco control. In this report, we update trends in youth and adult smoking prevalence. We find that while adult smoking prevalence has declined overall, socioeconomic gradients in smoking still persist within race and ethnic subgroups. In addition, we describe the diffusion of tobacco-control strategies at the national, state, and community level. Although recent developments, such as the Food and Drug Administration's (FDA) regulation of tobacco products, hold promise for tobacco control, there continues to be a need for broader dissemination of sustainably funded comprehensive national and state tobacco-control programs.

The in-situ, non-contact, and non-destructive measurement of the physicochemical properties such as the polarity of thin, hydrophilic polymer films is desirable in many areas of polymer science. Polarity is a complex factor and encompasses a range of non-covalent interactions including dipolarity/polarizability and hydrogen bonding. A polarity measurement method based on fluorescence would be ideal, but the key challenge is to identify suitable probes which can accurately measure specific polarity related parameters. In this manuscript we assess a variety of fluorophores for measuring the polarity of a series of relatively hydrophilic, thermoresponsive N-isopropylacrylamide/N-tert-butylacrylamide (NIPAM/NtBA) copolymers. The emission properties of both pyrene and 3-Hydroxyflavone (3-HF) based fluorophores were measured in dry polymer films. In the case of pyrene, a relatively weak, linear relationship between polymer composition and the ratio of the first to the third vibronic band of the emission spectrum (I(1)/I(3)) is observed, but pyrene emission is very sensitive to temperature and thus not suitable for robust polarity measurements. The 3-HF fluorophores which can undergo an excited-state intramolecular proton transfer (ESIPT) reaction have a dual band fluorescence emission that exhibits strong solvatochromism. Here we used 4'-diethylamino-3-hydroxyflavone (FE), 5,6-benzo-4'-diethylamino-3-hydroxyflavone (BFE), and 4 -diethylamino-3-hydroxy-7-methoxyflavone (MFE). The log ratio of the dual band fluorescence emission (log (I(N*)/I(T*))) of 3-HF doped, dry, NIPAM-NtBA copolymer films were found to depend linearly on copolymer composition, with increasing hydrophobicity (greater NtBA fraction) leading to a decrease in the value of log (I(N*)/I(T*)). However, the ESIPT process in the polymer matrix was found to be irreversible, non-equilibrated and occurs over a much longer timescale in comparison to the results previously reported for liquid solvents.

Laser use for rapid prototyping of microfluidic devices has proven useful but can have certain drawbacks including variations in channel width, depth and shape when producing complex geometries. We describe our work on an advanced rapid laser prototyping technique, based on the use of an “intelligent pinhole” and 193 nm excimer laser. The pinhole, a dynamic mask, consists of four individually programmable blades and is controlled through a LabVIEW user interface. Each blade has the capability to be positioned with sub-micron repeatability with a response time on the order of 5 ms. Synchronization with the excimer laser software allows the fabrication of more complex microchannel layouts that are not possible with fixed mask techniques. Using the programmability of the pinhole we can eliminate some of the undesirable effects associated with scanning laser ablation, such as ramps leading into and out of microchannels and banking or undercutting effects at microchannel junctions and corners. The paper will demonstrate beam re-configuration techniques which allow the creation of zero lead-ins to microchannels and show the system’s potential to rapidly generate varying design iterations by fabricating a working microfluidic device and testing its application.Laser use for rapid prototyping of microfluidic devices has proven useful but can have certain drawbacks including variations in channel width, depth and shape when producing complex geometries. We describe our work on an advanced rapid laser prototyping technique, based on the use of an “intelligent pinhole” and 193 nm excimer laser. The pinhole, a dynamic mask, consists of four individually programmable blades and is controlled through a LabVIEW user interface. Each blade has the capability to be positioned with sub-micron repeatability with a response time on the order of 5 ms. Synchronization with the excimer laser software allows the fabrication of more complex microchannel layouts that are not possible with fixed mask techniques. Using the programmability of the pinhole we can eliminate some of the undesirable effects associated with scanning laser ablation, such as ramps leading into and out of microchannels and banking or undercutting effects at microchannel junctions and corners. The paper will d...

Thin polymer films are important in many areas of biomaterials research, biomedical devices, and biological sensors. The accurate in situ measurement of multiple physicochemical properties of thin polymer films is critical in understanding biocompatibility. polymer function, and performance. In this work we demonstrate a facile spectroscopic methodology for accurately measuring the micro-polarity and hydrogen-bond donor/acceptor ability for a series of relatively hydrophilic thermoresponsive copolymers. The micro-polarity of the N-isopropylacrylamide (NIPAM) and N-tert-butylacrylamide (NtBA) co-polymers was evaluated by means of the E-T(30), alpha, beta, and pi* empirical solvatochromic polarity parameters. The data shows that increasing the NtBA fraction in the dry copolymer film reduces polarity and hydrogen-bonding ability. Within the Kamlet-Taft polarity, framework, the NIPAM/NtBA copolymer films are strong hydrogen-bond acceptors. strongly dipolar/polarizable and rather moderate hydrogen-bond donors. This characterization provides a more comprehensive physicochemical description of polymers, which aids the interpretation of film performance. Comparison of the measured E-T(30) values with literature data for other water-soluble polymers show that dry NIPAM/NtBA copolymers are slightly more polar than poly(ethylene oxide), less polar than polyvinylalcohol and approximately the same polarity as poly(N-vinyl-2-pyrrolidone), These findings indicate that this spectroscopic method is a facile, rapid, and nondestructive methodology for measuring polymer properties in situ, suitable for most biomaterials research laboratories. Higher Education Authority Programme for Research in Third Level Institutions, Science Foundation Ireland Grant (number 02/IN.1/M231) peer-reviewed

In this paper we investigate the passivating effects of exposing a freshly etched GaAs(100) surface to hydrogen sulphide gas. The effectiveness of this passivation procedure is assessed in a comparison between the characteristics of the treated and untreated surface by a range of techniques. Spectra of the treated surface obtained by deep-level transient spectroscopy reveal a significant reduction in the intensity of a peak attributed to interface states, which is clearly detected on the untreated surface. The idealities of the diodes fabricated on the treated surface are comparable with those obtained for diodes fabricated on the freshly etched GaAs(100) surface. Both photoluminescence and Raman spectroscopy measurements also indicate a reduction in the interface state densities of the treated surface compared with the untreated surface. Variations in the effectiveness of the passivation were observed, which appear to depend on the precise procedure followed during the preparation of the surfaces prior to hydrogen sulphide exposure.

The technique of Raman scattering at room temperature, is used to investigate the effect of H 2 S passivation of the surface of n-type GaAs. Well-defined LO, L - and L + features are distinguished in spectra which have been recorded in z ( x, y )[ovbar|zovbar] scatte ring orientation. It is observed that the ratio of the LO to L - peak is reduced by the effects of the passivation process and that the shift of the L + feature from the laser line is decreased. This latter effect, it is suggested, is caused by a decrease in free-carrier concentration due to donor neutralization by hydrogen during passivation. This neutralization effect will also affect the LO to L - ratio and so complicate a quantitative analysis of the influence of passivation on the surface barrier potential.

This essay suggests approaches to two issues of importance to the future of tobacco use control research. First, there is need to identify those areas of tobacco use prevention and cessation research which have evolved to the point where additional investigation would only bring incremental gains. The reduction potential of this research should then be consolidated by applying existing, effective interventions widely and systematically. Conversely, there is need to identify those areas in which additional research is necessary. Second, the most logical way to reach agreement on those areas which are ready to move from research to applications-of-research is, with the co-operation and advice of the research community, through the large funding organizations which have supported this research over the past 2 decades. It is these organizations which, once the most effective interventions are identified, are capable of supporting the centrally-planned, consensus-driven, comprehensive approaches to tobacco use control which will be necessary to continued success in reducing tobacco-related morbidity and mortality in the industrialized world and to begin addressing the growing problems of tobacco use in the developing world.

The National Cancer Institute's efforts to prevent tobacco-related cancers have resulted in numerous activities to reduce smoking prevalence throughout the United States. Two decades of research activity has provided much of the information needed for interventions through channels such as mass media, physician/dentist training, self-help strategies, and school-based prevention programs. However, in the area of adolescent tobacco-use reduction, it has been consistently observed that youth who have the highest tobacco-use rates are among those least likely to be reached through school-based or other programs. Thus, these youth, often labeled “high-risk,” are seen as a cornerstone for tobacco use prevention efforts. Although they pose a particularly difficult access problem, many valuable recommendations for strategies to identify and reach this group were made by a recent NCI-convened Expert Advisory Panel on the Prevention and Cessation of Tobacco Use by High-Risk Youth. The Panel considered this issue from three perspectives—methods of identifying these youth, strategies for reaching them with appropriate tobacco-use prevention/cessation programs, and identification of research needs. Their recommendations and conclusions are summarized in this article. Support for research addressing the prevention and cessation of tobacco use among high-risk youth is currently being considered by the NCI.

A coincidence in energy of the 2E and 4T2 excited levels of Cr3+ appears to occur in the material GSGG:Cr3+, and as a result the material exhibits a number of interesting luminescence features. The mixing of the 2E and 4T2 eigenstates by the spin-orbit coupling operator is analyzed using a simple model which takes account of the vibrational nature of the eigenstates. It is shown that this model is capable of explaining many of the observed luminescence features of the material.

Luminescence and lifetime measurements are presented for a new emission band in Fe-doped LiGa5O8. The emission is assigned to the 4 T 1 ( 4 G )→ 6 A 1 ( 6 S ) transition in the d5 configuration for Fe3+ ions in octahedral sites. Good-quality single-crystal samples allow fine structure in the zero-phonon line and in the sideband to be resolved.

We have observed a new broad-band luminescence, with a peak at 626.5 nm, additively-coloured BaF 2 , but only when exciting on the long wavelength side of the F-centre absorption band. Such emission could originate in one of the many complex centres which are created in such materials by additive colouration. However, the special conditions required for its observation as well as the mirror-image symmetry of the emission band with respect to the F-centre absorption band suggest that the emission may originate in isolated F-centres. To our knowledge, such emission has not been reported for any of the alkaline-earth fluorides.

Laser action, tunable around 1.2 μm, has been reported in Cr-activated forsterite (Mg 2 SiO 4 ). We have examined the emission from this material in the region 650–850 nm via photoluminescence, excitation and lifetime studies over a range of temperature. Our measurements indicate that the emission in this region can be assigned to transitions on Cr 3+ ions in high-field octahedral sites. The emission from the M1 site is clearly identified. We propose a simple model to account for the temperature dependence of the luminescence.

There has been considerable recent effort aimed at realising tunable near-infrared laser action in solid-state media. Beyond 1 μm Ni2+ and Co2+ emissions have been mainly studied, and laser action has been achieved in several materials doped with these ions although usually only at low temperatures. Luminescence from Co2+ and Ni2+ in the host material LiGa5O8 is described and evidence is presented for a high quantum efficiency, even up to room temperature. We describe also the results of our lifetime and luminescence measurements on the various active centres in the Mg2SiO4: Cr laser system.

Laser Induced Periodic Surface Structures (LIPSS) may have numerous applications, ranging from biomaterial applications to LCDs, microelectronic fabrication and photonics. However, in order to control the development of these structures for their particular application, it is necessary to understand how they are generated. We report our work on investigating the melting that occurs during LIPSS formation. LIPSS were generated on three polymer surfaces - polyethylene terephthalate (PET), amorphous polycarbonate (APC) and oriented crystalline polycarbonate (OPC) - which were irradiated with a polarized ArF excimer laser (193 nm) beam with fluences between 3 and 5 mJ/cm 2 . The structures were imaged using a Transmission Electron Microscope (TEM), which facilitated investigation of changes in the polymer structures and consequently the depth of the melt zone that accompanies LIPSS generation. We also present theoretical calculations of the temperature-depth profile due to the interaction of the low fluence 193 nm laser beam with the polymer surfaces and compare these calculations with our experimental results.

A solid-state UV laser was used to make arrays of reproducible percussion-drilled micron-sized holes in polyimide. An optical switch was employed as a pulse picker to select specific patterns of pulses from the high repetition rate laser beam. The ability to control and vary the number of pulses per burst and the time between bursts enhanced the drilling rate while minimizing thermal damage around the holes. The optimum pulse patterns were determined experimentally. A photodiode acted as a breakthrough sensor to end the drilling and optimize the exit hole size and quality. Results were compared with computer simulations of the drilling process based on modeling of the laser/material interaction.

The use of a water assist has been shown to improve machining efficiency and feature cleanliness for the laser micro machining of features in silicon. However, the water assist has been shown to have some disadvantages, including the fact that it dissolves protective coatings on semiconductor wafers and it tends to cause blockages in the debris extract system. Protective coatings dissolve because they are typically water-based in order to facilitate their removal after machining and therefore they are not compatible with the water assist process. Blockages in the extract system are due to the deposition of silicon debris, which does not remain adequately entrained in the water flowing through the extract system. This paper describes the use of oil assist instead of water assist to solve these problems while maintaining the advantages of water assist. Unlike water, which is polar in nature, oil does not dissolve the water-based coating. Due to the properties of the oil assist, the debris does not tend to deposit on the surfaces of the extract system so blockages are avoided. Suitable oils include industrial oils like Castrol Carecut and common vegetable oils like grape seed oil or olive oil.The use of a water assist has been shown to improve machining efficiency and feature cleanliness for the laser micro machining of features in silicon. However, the water assist has been shown to have some disadvantages, including the fact that it dissolves protective coatings on semiconductor wafers and it tends to cause blockages in the debris extract system. Protective coatings dissolve because they are typically water-based in order to facilitate their removal after machining and therefore they are not compatible with the water assist process. Blockages in the extract system are due to the deposition of silicon debris, which does not remain adequately entrained in the water flowing through the extract system. This paper describes the use of oil assist instead of water assist to solve these problems while maintaining the advantages of water assist. Unlike water, which is polar in nature, oil does not dissolve the water-based coating. Due to the properties of the oil assist, the debris does not tend to d...

Luminescence emission and excitation spectra of a number of natural spodumene crystals have been measured at temperatures down to 12 K. Both Cr3+ and Mn2+ centres were identified; Mn2+ is shown to be mainly in Li-sites rather than Al-sites and gives rise to a broad emission centred at 600 nm. In most spodumenes Cr3+ R-line emission with phonon sideband is observed at temperatures below 100 K. In the more Mn-rich crystals multiple R1 lines are seen at temperatures below about 40 K, but in Cr-rich crystals only one r1 line is observed and Cr3+ emission is evident at room temperature.

Fused biconic tapered (FBT) couplers are essential components in today's telecommunications networks where they are used for a number of different applications. The manufacturing process consists of aligning two adjacent fibres from which the buffer has been stripped, and subsequently heating and stretching them, creating an input taper, output taper either side of the fused coupling region. It is the coupling region where energy transfer between cores is possible; this gives the device its main characteristics, and the basic geometry can be used to create a range of devices such as 3 dB splitters, tap couplers, WDMs, etc. Low losses for these devices are achievable if made with reference to the adiabatic approximation. In this paper we report the development of a laser-based rig for the manufacture of couplers in which a CO2 laser replaces the gas torch typically used as a heat source in modern manufacturing processes. In addition to the use of a laser source, we describe the integration of advanced optical techniques and feedback mechanisms to improve the workstation's reliability and flexibility. These characteristics should be advantageous for efficient manufacture of standard devices and novel devices for niche applications.

Polymers play an important role in many applications such as microelectronics and medical devices. Micro-channels and shaped holes can be produced by 2.5D micro-structuring with excimer laser sources using mask projection. The industrial cost associated with these processes can be greatly reduced by the use of solid-state lasers due to their lower cost and maintenance. For this purpose, we investigate the interaction of polyimide (Kapton) with solid-state lasers emitting in the UV (266 & 355 nm) spectral range. The study presents a comparison of the ablation profiles obtained for different laser sources and these are discussed in term of roughness and efficiency. Limitations on the actual motion system (scan-head) are evident and the need to control the material removed by a small Gaussian beam in terms of overlapping for the direct writing process will be highlighted.

Percussion drilling of blind holes and vias in Kapton film was investigated using Q-switched solid state lasers operating at UV (355nm) and VUV (266nm) wavelengths. Holes were analyzed using different methods such as scanning electron microscopy (SEM) and surface profilometry. Ablation rates for the two wavelengths are compared. No abrupt thresholds were found and there was no evidence of an incubation effect within the first few pulses. Introducing pauses during the drilling increased the number of shots required for perforation of the film. The effects of fluence on diameter, depth and taper of the holes are presented. Smaller and neater holes are achieved more accurately with a lower fluence. An observed skin effect brought about by long exposure to low fluence VUV laser light is also discussed.

Excimer based laser ablation of micro-fluidic circuits for micro-total analysis systems (μTAS) is an alternative to more expensive techniques of LIGA or micro-moulding. In the interests of developing a rapid prototyping method for direct writing of micro-fluidic circuits in polymer materials the ablation process was characterised using Design of Experiment techniques and a robust full factorial model was developed. Input factors of pulse energy, repetition rate, scan speed and number of passes were considered. Output responses of trench bottom width, sidewall angle, trench depth and trench roughness were measured. From this a prediction equation was created to forecast the output responses prior to machining and to allow the development of a process prior to machining. The accuracy of the prediction equation is discussed for four materials; Polystyrene, Polycarbonate, Non-CQ grade PMMA and CQ grade PMMA. For the four materials studied the response of Polystyrene and Polycarbonate were similar while the two grades of PMMA behave differently.

A time-resolving Langmuir probe has been used to study the plasma plumes produced by ablation of silver with 200 femtosecond laser pulses at fluences of 1-12 J cm-2 at a central wavelength of 775 nm. Initial results have shown that surface contamination, and subsequent recontamination, can significantly influence the time of flight (TOF) signals obtained using the Langmuir probes. Surface conditioning techniques have been developed to overcome these influences. The TOF signals have been used to establish that the threshold fluence for the laser produced plasma in silver, under the present operating conditions, occurs at 1.04 J cm-2. The angular dependence of the magnitude of the ion yields and energies, at the time when the ion flux is maximized, agree with the predictions of Anisimov’s self-similar isentropic model of the plasma expansion.

UV and VUV laser ablation of micro-fluidic circuits for micro-total analysis systems (μTAS) is an alternative to more expensive techniques of LIGA or micro-moulding. The machining of trenches in PS, PC, PMMA (CQ grade and non-CQ grade) was investigated using two Q-switched solid state lasers, one operating at 266nm (fourth harmonic) and another at 355nm (third harmonic). These results were compared with results achieved using a 193nm Excimer laser. The structuring of the channels depends on both the laser wavelength and the target material. A comparison of the process will be presented with respect to the structure quality and efficiency of the process.

The use of designed polymer coatings for specific applications such as drug delivery or modifying cell response is a critical aspect of medical device manufacturing. The chemical composition and physical characteristics of thin polymer coatings need to be analysed in-situ and this can present difficulties for traditional analytical methods. For example, changes in the polarity of polymer coatings are typically measured using the contact angle (CA) method. This is a simple process and gives good results however; it cannot be used to measure very hydrophilic polymers, or to analyse features smaller than a couple of mm in size. There is a need for a non-contact method for polarity measurement that is suitable for hydrophilic polymers on a macro- and microscopic scale. 4'-diethylamino-3-hydroxyflavone (FE), 5, 6-benzo-4'-diethylamino-3-hydroxyflavone (BFE), and 4'-diethylamino-3-hydroxy-7-methoxyflavone (MFE) are fluorescence probes based on 3-hydroxyflavone. They respond to environment perturbations by shift and changes in the relative intensity of two well-separated bands in the emission spectra. These bands originate from an excited state intramolecular proton transfer (ESIPT) reaction. We have incorporated FE, BFE, and MFE into a novel thermoresponsive hydrophilic/hydrophobic copolymer system (NIPAM-NtBA) and studied its fluorescence behaviour. The fluorescence emission spectra depend strongly on copolymer composition, with increasing hydrophobicity (greater NtBA fraction) leading to a decrease in the value of log (IN*/IT*). This allows for the non-contact, measurement of the exact composition and surface energy of the copolymer system.

Typical applications of ultra-high-power femtosecond lasers include precision drilling and surface micro-machining of metals, and micro-structuring of transparent materials. However, high peak-power pulsed lasers are difficult to focus close to the diffraction limit because of aberrations that induce deviations from a perfect spatial wave-front. The sources of these aberrations include thermally induced and nonlinear optical distortions, as well as static distortions such as those introduced by gratings used in chirped-pulse amplification (CPA). A spatially clean beam is desirable to achieve the highest possible intensity on-target, and to minimize the energy deposited outside the central focus. One way to achieve this is to correct the wave-front using an adaptive optical element such as a deformable mirror, a more cost-effective solution than increasing peak intensity by providing further pulse amplification. The wave-front of the femtosecond system is measured using a Hartmann-Shack wave-front sensor, and corrected with a 37-channel deformable membrane mirror used slightly off-axis. The deformable mirror has been tested with a FISBA OPTIK μPhase HR digital interferometer, which is also used to calibrate the performance of the wave-front sensor. The influence of fluctuations of the laser on the measurement is minimised by averaging the centroid positions obtained from several consecutive frames. The distorted wave-front is compared to a reference flat wave-front which is obtained from a collimated laser diode operating at the same wavelength as the femtosecond system. The voltages on the deformable mirror actuators are then set to minimise the difference between the measured and reference wave-fronts using a simple least squares approach. Wave-front sensor and correction software is implemented in Matlab.

The problem created by the re-deposition of ablated material when laser machining structures in silicon wafers is investigated. The study focuses on the specific case of machining wafer grade silicon with femtosecond pulses centered at a wavelength of 775 nm. Based on the evidence that a highly ionised plasma state exists immediately after laser ablation, this work explores the potential of using electric fields to channel the debris out of the laser machined feature before it becomes deposited. To this extent the work discusses the step-by-step development of different experimental arrangements, by first evaluating its effects, then identifying its limitations and finally by proposing and investigating potential solutions. It is found that a reduction in the amount of re-deposited debris is observed when a carrier-depleted region is generated in silicon materials.

Hydrocarbon-bearing fluid inclusions (HCFI) are microscopic cavities within rocks that are filled with petroleum oil, the composition of which may not have changed since the trapping event. Thus, the composition of that entrapped oil can provide information about the formation and evolution of the oil reservoir. This type of information is important to the petroleum production and exploration industries. Crude oil fluorescence originates from the presence of cyclic aromatic compounds and the nature of the emission is governed by the chemical composition of the oil. Fluorescence based methods are widely used for analysis of crude oil because they offer robust, non-contact and non-destructive measurement options. The goal of our group is the development of a non-destructive analytical method for HCFI using time-resolved fluorescence methods. In broad terms, crude oil fluorescence behavior is governed by the concentration of quenching species and the distribution of fluorophores. For the intensity averaged fluorescence lifetime ( τ ), the best correlations have been found between polar or alkane concentrations, but these are not suitable for robust, quantitative analysis. We have recently started to investigate another approach for characterizing oils by looking at Time-resolved Emission Spectra (TRES). TRES are constructed from intensities sampled at discrete times during the fluorescence decay of the sample. In this study, TRES, from a series of 10 crude oils from the Middle East, have been measured at discrete time gates (0.5 ns, 1 ns, 2 ns, 4 ns) over the 450-700 nm wavelength range. The spectral changes in TRES, such as time gate dependent Stokes shift and spectral broadening, are analyzed in the context of energy transfer rates. In this work, the efficacy of using TRES for fingerprinting individual oils and HCFI is also demonstrated. National Center for Biomedical Engineering Science as part of Higher Education Authority’s Programme for Research in Third Level Institutions. Not

The analysis of entrapped debris provides a useful complementary method of investigating the laser ablation mechanism in laser processing of polycrystalline metal samples using a femtosecond laser (Clark MXR, CPA2001). Morphological investigations of the laser- processed areas, for a range of laser fluences and pulse number, were recorded using optical and scanning electron microscopies (SEM) and white light interferometry. Data obtained on ablation rates, ejected particle sizes, and crater morphologies prove that ablation changes from a smooth to an explosive process at high fluences, as identified with changes in the material removal mechanisms. The build-up of laser-induced mechanical stresses, due to the heating and cooling of the samples between successive laser shots, plays an important role in the material modification process, leading to the observed dependence of ablation threshold on shot number. The strength of the dependence is governed by the incubation coefficient, S, which has been measured for all materials studied. In this paper, additional insight is derived from the analysis of the debris generated for metal samples, which can be attributed to laser ablation mechanisms based on vaporization, spallation, phase explosion, and fragmentation.

Journal article Time-resolved fluorescence data was collected from a series of 23 bulk crude petroleum oils and six microscopic hydrocarbon-bearing fluid inclusions (HCFI). The data was collected using a diode laser fluorescence lifetime microscope (DLFLM) over the 460-700 nm spectral range using a 405 nm excitation source. The correlation between intensity averaged lifetimes (T) and chemical and physical parameters was examined with a view to developing a quantitative model for predicting the gross chemical composition of hydrocarbon liquids trapped in HCFI. It was found that T is nonlinearly correlated with the measured polar and corrected alkane concentrations and that oils can be classified on this basis. However, these correlations all show a large degree of scatter, preventing accurate quantitative prediction of gross chemical composition of the oils. Other parameters such as API gravity and asphaltene, aromatic, and sulfur concentrations do not correlate well with T measurements. Individual HCFI were analyzed using the DLFLM, and time-resolved fluorescence measurements were compared with T data from the bulk oils. This enabled the fluid within the inclusions to be classified as either low alkane/high polar or high alkane/low polar. Within the high alkane/low polar group, it was possible to clearly discriminate HCFI from different locales and to see differences in the trapped hydrocarbon fluids from a single geological source. This methodology offers an alternative method for classifying the hydrocarbon content of HCFI and observing small variations in the trapped fluid composition that is less sensitive to fluctuations in the measurement method than fluorescence intensity based methods. Higher Education Authority; Bank Zachodni/Allied Irish Bank (fellowship MAP); Science Foundation Ireland (Grant no. 02/IN.1/M231); Enterprise Ireland Research Innovation Fund (grant no. IF/2001/061) peer-reviewed

The aim of the current work is two-fold: First, the aim is to investigate the transition, for a number of metals, from a smooth ablation process to an explosive one. Secondly we aim to study the dependence of the ablation threshold in metals on the applied laser shot number. Ablation of polycrystalline metal samples was performed with multiple pulses from a femtosecond laser (Clark MXR, CPA2001). Mor phological investigations of the laser processed areas were recorded using optical and scanning electron microscopies (SEM) and white light interferometry. The investigations have been carried out on sample matrices which were processed for a range of laser fluences and applied laser shots for four metals. Data obtained on ablation rates, ejected particle sizes and crater morphologies prove that ablation changes from a smooth to an explosive process at high fluences, as identified with changes in the material removal mechanisms. Threshold fluences were measured for both the smooth and explosive ablation processes. The ablation threshold fluence depends on the number of pulses applied to the same spot. It was found that the build up of laser induced mechanical stresses, due to the heating and cooling cycles of the samples between consecutive laser shots, plays an important role in the material modification process. It leads to the observed dependence of ablation threshold on shot number, which is described by a power law based on a mechanical fatigue model. The strength of the dependence is governed by the incubation coefficient, S, which has been measured for all materials studied. It is expected that the build up of laser energy or incubation leads to the accumulation of material defects and residual stresses which has the effect of lowering the energy required to cause ablation using a large number of incident laser shots. Keywords: femtosecond pulse laser, ablation threshold, material removal mechanisms, laser materials processing, metals. 1. INTRODUCTION Ultrashort pulsed laser ablation has become a very active area of research in recent years. It is definitely one of the most industrially driven technologies to have arisen from femtosecond laser applications because, through careful tailoring of the appropriate parameters, it allows practically any material to be processed with extremely high precision and with minimal collateral damage. By depositing the laser energy into the electrons of the material on a time-scale which is short compared with the transfer time of this energy to the bulk of the material, the ablation efficiency is improved and the ablation threshold is reduced and more well defined. The fundamental physical mechanisms of material removal during laser ablation are not clearly understood as yet

The performance of a polymeric biomaterial depends on the bulk and surface properties. Often, however, the suitability of the surface properties is compromised in favour of the bulk properties. Altering the surface properties of these materials will have a profound effect on how cells and proteins interact with them. Here, we have used an excimer laser to modify the surface wettability of nylon 12. The surface treatment is rapid, cost-effective and can cause reproducible changes in the surface structure of the polymers. Polymers were treated with short wavelength ( < 200 nm) UV light. These wavelengths have sufficient photon energy (6.4eV) to cause bond scission at the material surface. This results in a surface reorganisation with incorporation of oxygen. Surface wettability changes were confirmed using contact angle measurements. Cell interactions with the surfaces were examined using 3T3 fibroblast and HUVEC cells. Cells morphology was examined using a confocal laser scanning microscope (CLSM). Cell activity and cell number on the treated nylon were assessed using biochemical assays for up to seven days. Both fibroblasts and endothelial cells initially proliferated better on treated compared with untreated samples. However, over seven days activity decreased for both cell types on the control samples and endothelial cell activity and cell number also decreased on the treated polymer.

The generation of debris is critical in the future application of laser technology in IC, MEMS, MOEMS manufacture. Re-deposition of debris is also critical in optimising throughput of multi-pass laser ablative processes. In this study, the debris formed in laser micromachining of wafer grade silicon is investigated. Details of the laser workstation, based on a UV DPSS laser, will be presented and the development of real time diagnostic capabilities and off-line techniques will then be described. A real time imaging capability has been used to monitor plasma and shock front propagation with nanosecond resolution. The detection system is also used to monitor spectral emission of debris and micron-sized particulate ejected from the silicon surface. Emission spectroscopy of the laser ablated silicon in the plasma show spectral features that are characteristic of atomic and molecular species on timescales of nanoseconds and microseconds, respectively, after the laser pulse. Off-line characterisation techniques have focused on investigating the distribution and chemical composition of entrapped particulate. A number of novel experimental configurations for particulate entrapment, both adjacent to and remote from the laser-ablated surface, will be described. EDX results indicate that debris generated in air is composed principally of oxygen and silicon. Additional SEM results indicate that the particulate size grows through aggregation and depends on the environment in which they are generated.

Femtosecond laser micromachining of silicon offers the potential to realize precision components with minimal thermal damage. In this work, an assessment of the damage observed in bulk silicon during femtosecond laser micromachining is presented. The different analysis methods used to determine the structural and chemical changes to wafer grade silicon is first described. The analysis is at or above the ablation threshold - defined as the point where laser induced crystalline- damage is first observed for 1 kHz laser pulses, of 150 fs duration, at a wavelength of 775nm. Structural analysis is based upon electron and optical microscopies, with different sample preparation techniques being used to reveal the micro-machined structure. A key feature of the work presented here is the high-resolution Scanning Transmission Electron Microscope (STEM) images of the laser-machined structures. Below the ablation threshold, electrical experiments were performed with silicon under femtosecond laser excitation to provide a direct method for determining the accumulation of damage to the silicon lattice. Based on this analysis, it will be shown that laser machining of silicon with femtosecond pulses can produce features with minimal thermal damage, although lattice damage created by mechanical stresses and the deposition of ablated material both limit the extent to which this can be achieved, particularly at high aspect ratios.

Collectively, cardiovascular disease (including stroke), cancer, and diabetes account for approximately two thirds of all deaths in the United States and about $700 billion in direct and indirect economic costs each year. Current approaches to health promotion and prevention of cardiovascular disease, cancer, and diabetes do not approach the potential of the existing state of knowledge. A concerted effort to increase application of public health and clinical interventions of known efficacy to reduce prevalence of tobacco use, poor diet, and insufficient physical activity—the major risk factors for these diseases—and to increase utilization of screening tests for their early detection could substantially reduce the human and economic cost of these diseases. In this article, the ACS, ADA, and AHA review strategies for the prevention and early detection of cancer, cardiovascular disease, and diabetes, as the beginning of a new collaboration among the three organizations. The goal of this joint venture is to stimulate substantial improvements in primary prevention and early detection through collaboration between key organizations, greater public awareness about healthy lifestyles, legislative action that results in more funding for and access to primary prevention programs and research, and reconsideration of the concept of the periodic medical checkup as an effective platform for prevention, early detection, and treatment. ( Stroke . 2004;35:1999-2010)

A randomised trial evaluated the American Cancer Society's telephone counselling service to assist smoking cessation. Counselling nearly doubles a smokers' odds of quitting and maintaining cessation for one year. The estimated cost for each case of maintained smoking cessation attributable to counselling availability is approximately 1300 dollars.