Laser Induced Breakdown Spectroscopy LIBS is a fast non-contact technique for the analysis of the elemental composition using spectral information of the emission from a laser-induced plasma. For the LIBS studies in this thesis the focus has been in using very low energy, microjoule pulses in order to give high spatial resolution and minimize the laser system requirements. This is a regime that we refer to as microLIBS. Under such conditions it is important to maximize the signal detected to give the lowest limit of detection LOD possible. One technique to improve the signal to noise ratios is by coupling LIBS with Laser Induced Fluorescence. This is a technique where the _rst pulse creates a vapor plume and the second pulse tuned to a resonant absorption line of the species of interest re-excites the plume. We term this technique as Laser ablation Laser Induced Fluorescence LA-LIF. We have been investigating the performance of LA-LIF at low pulse energies (_ 1 mJ for both pulses) for the detection of elemental contaminants in water. This technique allows reasonable performance compared to high energy singlepulse LIBS, but at a much reduced total energy expenditure. This allows LODs in the parts per billion range ppb range which typically cannot be obtained with low energy single pulse probing of the systems. This approach or exceeds the sensitivities which can be obtained with many shots using much larger energy systems. In this thesis we investigated the performance of LIBS at low pulse energies for the detection of Pb as a contaminant in water. An LOD of 70 ppb was obtained for an accumulation of 100 shots with the ablation laser pulse energy of 250 _J and an excitation laser pulse energy of 8 _J. A systematic study of the detector conditions was made for the system for the detection of Pb. Scaling laws for the LOD in terms of the pump and probe energies were measured and also the e_ect of detector gain, the gate delay and the gate width were studied. In this thesis LIBS and LA-LIF were also used to analyze ultralow volumes of analyte in liquids in microuidic geometries. LIBS was applied for the detection of Na in liquid droplets in a microuidic system. The detection of Na as low as 360 femtograms was demonstrated for 100 shots integrated in this system. An LOD of 7 ppm for Pb for 100 shot accumulation was demonstrated using the LA-LIF technique on an 18 _m diameter microdroplet. To study the laser interaction with the water targets the MEDUSA one dimensional hydrocode was used. The propagation of the shockwave and plume dynamics were studied using this modeling code. The expansion of the plume was studied and compared to experimentally measured values and to physical models for blast wave expansion and stagnation. Two preconcentration techniques were also studied, one of which used a wood-chip as a substrate to absorb the analyte liquid and wick the salt on to the surface for analysis and the other used an electroplating technique to plate the analyte metal as a thin _lm on a substrate metal used as a cathode. The electroplating method for preconcentration was also studied using a microchip laser and a LOD of 6.4 ppb for Pb in water was obtained for an accumalation of 200,000 shots. / Photonics and Plasmas

Abstract The ratio of unemployment in 2000 is 2.99%. The ratio of unemployment in 2001 is 4.57%. The ratio of unemployment in 2002 is 5.17%(narrow sense). The ratio of unemployment in 2002 is 7.26% (broad sense). They achieve the highest record in history at the same time. Mention as above we know unemployment has become the most serious problem in Taiwan now. The top three motorcycle companies in Taiwan are KYMCO, SYM, and YAMAHA which have different business styles, so there must be some differences in design and practice of downsizing programs. Finding the same points and the differences in downsizing programs are the motives of this research. And forming experience rules for business to use can show the value of this research. On the other side, we can find manpower market problems in manufacturing industries in Taiwan from researching Taiwan motorcycle industries. The quantities method researches about quitting are very popular recently. Although the research contents can provide many ideas for business, the business truly needs the know-how of planning in advance and implementing steps in downsizing programs that are key factors whether the downsizing programs can smoothly succeed or not. But we seldom read such descriptive researches that business readers really want to consult. This research tries to discuss with process design and tasks of every stages of downsizing programs according to time axis. Secondary data are from newspapers, periodical, thesis, books, company publication, and network. Primary data come from case companies interview (the first step) and questionnaire (the second step). The objects who this researcher interviews are HR department managers of KYMCO, SYM, and YAMAHA. The in-depth interview of the first step¡Gthis research analyzes the origin of downsizing programs from business condition, gets together the practice process and situation of downsizing programs from history vestige, records the improved activities after downsizing programs from holding the present situation, and describes business vision from future chance. The questionnaire of the second step¡Gtry to understand the feeling that personnel matters workers feel at heart in carrying out downsizing programs, the opinions that personnel matters workers think about downsizing programs, the belief that decision-making managers have to personnel matters workers¡¦ professional performance in downsizing programs. From the comparison and analyses of interview data of case companies, we can clearly know the cause, entire process, and effect of downsizing programs of the top three motorcycle companies in Taiwan. At last this research submits the related proposals from different views¡Gthe proposal for employees (create high additional value), the proposal for government (create occupation advantage by improving political and economical environment), the proposal for business (laws side. human kindness side. management side. implementation side ), the proposal for case companies (strategy. internation. system. science and technology).

No description available.

Thesis (doctoral)--Uppsala University, 1983. / Includes bibliographical references (p. 26-33).

The term ‘tipping event’ is used to describe a certain class of phenomena as observed in many different fields of science. It refers to an event where a gradual change of external forcing causes a sudden, large, often unwanted, transition to the state of the system. Some examples of known tipping events in science include: Arctic sea ice melting (climate), epileptic seizures (biology), collapse of ecosystems and populations (ecology) and market crashes (finance). Three mathematical mechanisms for tipping events have been proposed in the literature: bifurcation-, noise- or rate-induced tipping. Recent research has focused on developing early-warning indicators to potentially offer forewarning, which can extract from output time series whether the external forcing approaches a critical level at which tipping occurs. Two commonly used early-warning indicators are an increase of autocorrelation and variance in the time series data for the system’s output. The theory behind the presence of these indicators is the loss of stability of the system’s current state known as ‘critical slowing down’ for the approach of a bifurcation-induced tipping. Rate-induced tipping occurs when the external forcing reaches a critical rate instead of level. For rate-induced tipping there is no loss of stability of the system’s current state and therefore it is not clear if the early-warning indicators should exist. In this thesis we investigate the presence of early-warning indicators for models that show rate-induced tipping with additive noise. We also explore a technique for determining the most likely time of tipping using optimal paths for escape. Research has mainly focussed on testing the early-warning indicators for examples of known tipping events in the past. The ultimate aim of early-warning indicators would be to have the ability to predict future tipping events. Using the early-warning indicators in isolation is susceptible to incurring false alarms and missed alarms. We present a method for approximating the probability of experiencing rate-induced tipping with noise for slow to moderate drift speeds.

Elevated concentrations of mercury in soils are quite hazardous to flora and fauna and water bodies near these soils. This makes continuous monitoring of mercury very essential. This work compares two potential spectroscopic methods LIBS and SIBS at their optimum experimental conditions for mercury monitoring. The experimental conditions for Hg measurements with LIBS and SIBS were determined and calibration was developed. The limits of detection (LODs) of Hg in soil were calculated from the Hg calibration curves. The LOD for mercury (Hg) in soil calculated using LIBS and SIBS are 483 parts-per-million and 20 parts-per-million, respectively. The present study indicates that SIBS is more efficient with powder samples in a low concentration region for quantification of mercury in soils while LIBS is efficient in the region of higher concentrations using pellet samples. Both these techniques can be further investigated and improved for in-situ analysis of soils.

The major target of ionising radiation has been determined as cellular DNA. Damage to DNA, as detected at 77K under conditions of direct damage by ESR, is localised on the bases thymine and guanine. This damage leads to single and double strand breaks, precursors of cell death and mutagenesis. In an attempt to intercept the damage at the bases, before formation of strand breaks, the use of polycations as potential drug delivery systems to DNA has been examined. Magnetic resonance techniques have been used to establish that polyamines used are present almost completely as polyammonium cations at pH 7 and to probe the interactions of a number of polycations with DNA. Sodium-NMR was used to investigate the affinity of polyamines, poly- aminothiols and transition-metal complexes for DNA, via sodium ion displacement from the DNA region. It was found that small metal complexes displace a greater number of sodium ions than polyamines of similar charge. Application of the counterion condensation theory led to a model of the counterions existing within a cylinder around the DNA of approximate radius 20A. The mode of interaction of polyammonium cations was studied using proton magnetic resonance. Linewidths, related to the transverse relaxation rate, give information on the motion of compounds close to DNA. Comparison of linewidths in the presence and absence of DNA revealed no significant broadening. This was interpreted as indicative of a loose, electrostatic interaction, not significantly hindering motion of the cations close to DNA, suggesting rapid motion of polyammonium ions along the DNA. The radioprotection of DNA by various transition-metal complexes was studied using ESR. Certain compounds exhibited protection via electron transfer, resulting in a decreased radical yield.

No description available.

No description available.

No description available.