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Arid ecosystems are very sensitive to a variety of physical, chemical and biological degradation processes. Tarim Basin, the biggest endorheic basin in the Central Asia continent, is considered as one of the least water-endowed regions in the world and arid and semi-arid environmental conditions are dominant. For the purposes of the convention, arid, semi-arid and dry sub-humid areas were defined as "areas, other than polar and sub-polar regions, in which the ratio of annual precipitation to potential evapotranspiration falls within the range from 0.05 to 0.65." In this study, the Aridity Index (AI), the ratio of precipitation and land surface temperature, was also adopted as the base method for determining dry land types and thereby delineating boundaries and showing changes of aridity conditions in Tarim Basin. Here, precipitation is from TRMM/PR, and land surface temperature is from Modis LST. To analyze the spatial and temporal variations of arid environmental conditions in Tarim basin, we calculated the yearly aridity index (the ratio of total yearly rainfall to yearly mean Land Surface Temperature) based on the accumulated monthly precipitation and the monthly Land Surface Temperature in growing season for the period 2000-2009. The results indicated it is possible to work out an aridity index map with more detailed spatial patterns, which is valuable for identifying human impacts by associated with vegetation and soil moisture characters.

Hydrological predictions in ungauged or poorly gauged basin are crucial for sustainable water management and environmental changes study induced by climate change. Application of remote sensing technology has retrieved lots of spatio-temporal dataset during the past decades for references. In this study, TRMM/PR and MODIS LST data were introduced to get spatial patterns of precipitation and temperature changes by Empirical Orthogonal Function (EOF) technique in a mountainous watershed, southern Tianshan. An input variable group was attempted to be constructed for the Artificial Neural Networks (ANN) to model the stream flow change based on the patterns achieved above. The results indicate that the spatial variability patterns of meteorology can be well recognized from the remote sensing data by EOF analysis. The stream flow process can be satisfyingly simulated with input variables captured from the leading modes during the study period. While, since the probabilistic model was not based on full physical mechanisms, and often times, also limited by the amount of input data, uncertainties often implicated in the output. As an example, it is discussed through the rapidly glaciers melting phenomena induced by climate warming, which is expected to cause change in the flow generation mechanism.

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.

The clinical application of a new developed fiber guided CO2 laser in soft tissue surgery will be demonstrated (wavelength 10.6 micrometers , pulse duration 5 ms up to cw, pulse repetition rate 1-99 Hz, maximum average power at the outlet of the handpiece 9.4 watts, focus diameter 0.3 mm, two confocal pilot laser beams; ASAH medico, Hvidovre, Denmark). In this study laser parameters were set to a pulse duration of 5 up to 20 ms and a maximum repetition rate of 20 Hz. Leukoplakia removal was done with a defocused beam, while for excisions and incisions the laser was used in focus. Excisions of fibromas, lipomas etc. were performed. Especially for gingiva extensions employing free gingival grafts this new laser device was engaged. After two weeks of wound healing all gingival graft procedures were successfully complete. Healing process following large vestibuloplasty procedures concerning a total jaw lasted as long as known from conventional techniques. For the daily clinical use in soft tissue surgery this fiber guided CO2 laser system appears to be a versatile and reliable tool.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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.

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.

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.

Transmissions spectra of healthy human arterial vessel wall (intima, media, adventitia), lipid plaque as well as calcified plaque were obtained from 245 autopsy specimens (25 patients) by znicrospectrophotometry (25 jim sections, wavelength 240 nm - 1070nm). Lipid plaques showed moderately increased optical density over normal tissue in the visible and near infrared spectral range with maximal values in the blue spectral range (440 nm to 530 nm). At these wavelengths, extinction was about a factor of S compared to intima, a factor of 3 higher than in media, and a factor of 7 higher with respect to adventitia. Over the whole spectral range investigated, calcified plaque exhibited a significantly higher optical density compared to all layers of normal vessel wall. The maximum differences were found between 300 and 450 am for intima (6 to 7 fold), between 440 and 1070 for media (3 fold) and above 550am for adventitia (10 to 12 fold).© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.