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Pulse Duration (pulse + duration)
Selected AbstractsTilt or Pulse Duration,Which is the Decisive Parameter in Defibrillation?PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 10 2007WERNER IRNICH Ph.D. No abstract is available for this article. [source] Variable-Pulse Nd:YAG Laser in the Treatment of Facial TelangiectasiasDERMATOLOGIC SURGERY, Issue 1 2006AVERY A. BEVIN MD BACKGROUND Variable-pulse 1,064 nm wavelength lasers have been used with good effectiveness on leg telangiectasias and reticular veins and have shown promising results on facial telangiectasias as well. OBJECTIVE To investigate the effectiveness of a variable-pulse neodymium:yttrium-aluminum-garnet (Nd:YAG) laser using a small spot size in the treatment of facial telangi-ectasias. METHODS Eight male patients (mean age 75 years) underwent a single treatment session using a variable-pulse 1.5 mm spot size Nd:YAG laser with epidermal cooling. Telangiectasia diameters were 0.3 to 2.0 mm. Test sites were performed using three pulse widths (3, 20, and 60 ms), with fluences varying depending on vessel size and response. Full treatments were per-formed using test parameters giving the best response. Thirteen weeks later, the patients returned for final evaluation and satisfaction rating. RESULTS Fluences ranged from 226 to 425 J/cm2, with smaller vessels requiring larger energies. Pulse duration was equally divided between the 20 and 60 ms settings. The shortest pulse width (3 ms) was inferior in all patients. Longer pulse durations achieved superior vessel elimination with minimal immediate purpura and no postinammatory hyperpigmentation. The average mean vessel clearance was 26 to 50% in half of the patients and 51 to 75% in the other half as evaluated by three unbiased dermatologists with extensive laser experience. CONCLUSION A small,spot size Nd:YAG laser using a pulse width of 20 ms or higher appears to be effective in clearing a significant percentage of facial telangectasias with a single pass. The side effects were minimal. [source] Treatment of Melasma Using Variable Square Pulse Er: YAG Laser ResurfacingDERMATOLOGIC SURGERY, Issue 3 2009RUNGSIMA WANITPHAKDEEDECHA MD BACKGROUND Treatment of melasma remains a challenge. Laser treatments show limited efficacy, with a high rate of recurrence and side effects. Recently, variable-pulsed erbium:yttrium aluminum garnet (Er:YAG) lasers have shown favorable results in skin resurfacing, with minimal downtime and adverse effects. OBJECTIVE To determine the efficacy and side effects of variable square pulsed (VSP) Er:YAG laser resurfacing for treatment of epidermal type melasma. METHODS Twenty Thai women with epidermal-type melasma were treated with two passes of VSP Er:YAG laser resurfacing using a 7-mm spot size, pulse duration of 300 ,s, and a fluence of 0.4 J/cm2. Two treatments were given 1 month apart. Visual analog scale (VAS), Melasma Area and Severity Index (MASI) score and melanin index (MI) were measured at baseline and 1, 2, and 4 months after treatment. RESULTS There was a significant improvement in VAS from baseline at 1-, 2-, and 4-month follow-up visits (p<.001). Significant improvement in MASI score at the 2-month visit from baseline (p=.004) was also observed. The average MI measured using melanin reflectance spectrometry measurements corresponded to MASI score rating. CONCLUSIONS VSP Er:YAG laser resurfacing effectively but temporarily improved epidermal-type melasma. Recurrence was observed after the treatment was discontinued. [source] Minimally Ablative Erbium:YAG Laser Resurfacing of Facial Atrophic Acne Scars in Asian Skin: A Pilot StudyDERMATOLOGIC SURGERY, Issue 5 2008YONG-KWANG TAY MD BACKGROUND Atrophic scars are dermal depressions caused by collagen damage most commonly occurring after inflammatory acne vulgaris. There are little published data regarding the effectiveness and safety of minimally invasive lasers in the treatment of atrophic acne scars in darker skin types. OBJECTIVE The purpose was to evaluate the efficacy and safety of a low-fluence 2,940-nm erbium:YAG laser in the treatment of atrophic acne scars in Asian patients. MATERIALS AND METHODS Nine patients aged 19 to 45 years with mild to moderate atrophic facial scars and Skin Types IV and V were treated with topical anesthesia and one to two passes with an erbium:YAG laser two times at 1-month intervals. Treatment parameters were 6-mm spot size, fluence of 400 mJ, pulse duration of 300 ,s, and repetition rate of 2 Hz. RESULTS At 2 months after the last treatment, mild to moderate clinical improvement was noted in all patients compared to baseline. Treatment was well tolerated. Side effects consisted of posttreatment erythema, peeling, and crusting, which resolved within 1 to 2 weeks. There was no postinflammatory hyper- or hypopigmentation, blistering, or hypertrophic scarring. CONCLUSION Low-fluence erbium:YAG facial resurfacing was effective and safe in patients with mild to moderately severe atrophic acne scarring. [source] Resurfacing of Different Types of Facial Acne Scar With Short-Pulsed, Variable-Pulsed, and Dual-Mode Er:YAG LaserDERMATOLOGIC SURGERY, Issue 4 2004Sang-Hyuk Woo MD Background. Laser skin resurfacing has become a popular therapeutic modality for the correction of acne scars, but it is not always effective in all types of acne scars. Objective. To evaluate the clinical effects of resurfacing with the short-pulsed Er:YAG laser, the variable-pulsed Er:YAG laser, and the dual-mode Er:YAG laser for each type of facial acne scars. Methods. One hundred fifty-eight patients with facial acne scars were included in this study. Eighty three patients (18 deep boxcar scars, 8 ice-pick scars, 11 rolling scars, and 46 shallow boxcars) were treated with the 350-,s short-pulsed Er:YAG laser at the setting of 12.5 to 15%/cm2. Thirty-five patients (8 deep boxcar scars, 4 ice-pick scars, 12 rolling scars, and 11 shallow boxcars) were treated with the variable-pulsed Er:YAG laser at the setting of 7.0 to 7.5%/cm2 and 7-ms pulse duration. Forty patients (8 deep boxcar scars, 4 ice-pick scars, 17 rolling scars, and 11 shallow boxcars) were treated with the dual-mode Er:YAG laser with 350-, ablation mode at 17.5%/cm2 and 8-ms coagulation mode at 3.15%/cm2. Facial photographs were obtained at baseline and at 2- to 4-week intervals postoperatively. Acne scars were classified into four types, and clinical improvements of facial acne scars were evaluated. Results. Resurfacing with the short-pulsed Er:YAG laser shows good to excellent results for ice-pick and shallow boxcar scars, fair to good for deep boxcar scars, and poor to fair for rolling scars. Resurfacing with the variable-pulsed laser shows good to excellent results for ice-pick and shallow boxcar scars, fair to good for deep boxcar scars, and good for rolling scars. Resurfacing with the dual-mode laser shows good to excellent results for ice-pick, shallow, and rolling scars and produced good results on deep boxcar scars. Conclusion. Shallow boxcar and ice-pick scars can be treated successfully using any types of Er:YAG laser. In cases of rolling and deep boxcar scars, however, Er:YAG laser with a long-pulse duration for a thermal effect is needed for successful treatment. [source] Collagen Remodeling After 585-nm Pulsed Dye Laser Irradiation: An Ultrasonographic AnalysisDERMATOLOGIC SURGERY, Issue 10 2003Brent R. Moody MD Background and Objectives. Nonablative dermal remodeling is an evolving technology that has generated great interest among both laser surgeons and patients. Evidence indicates that dermal collagen formation is the key mechanism of action for the nonablative techniques. We studied, with ultrasound, new collagen formation after nonablative laser irradiation. Methods. Ten patients with facial rhytids underwent a single treatment with a 585-nm pulsed dye laser. The patients were all female, ranging in age from 47 to 67, and were Fitzpatrick skin types I,III. Laser parameters were as follows: an energy fluence of 2.4 to 3.0 J/cm2, a pulse duration of 350 ,sec, and a spot size of 5 mm with no overlap. Ultrasonographic assessments of dermal collagen were taken at baseline and at 30 and 90 days after treatment. Results. Ultrasonography demonstrated an increase in dermal collagen after a single treatment with the 585-nm pulsed dye laser. The greatest degree of neocollagenesis occurred periocularly. Conclusion. A single treatment with a 585-nm pulsed dye laser appears to increase dermal collagen. This increase in dermal collagen can be assessed with noninvasive cutaneous ultrasound. [source] Multipass Treatment of Photodamage Using the Pulse Dye LaserDERMATOLOGIC SURGERY, Issue 7 2003Emil A. Tanghetti MD Background. Pulse dye lasers (PDLs) alter structural proteins in scars and photodamaged skin, in addition to their effects on dermal vasculature. The PDL has become an option in the treatment of photodamage. Although improvements to skin texture are generally modest when compared with ablative resurfacing, PDL offers a treatment with few side effects. A number of methods have been proposed in an effort to improve treatment outcomes. These range from single, low-fluence treatment with no purpura to multiple passes and treatment sessions as well as purpuric doses. Objective. To evaluate several of the PDL treatment methods to improve photorejuvenation outcomes while limiting the risk of side effects. Methods. Twenty patients with photodamage were separated into two groups. Each group received a series of four single-pass treatments or four double-pass treatments at 2-week intervals. Treatments were done using a 595-nm PDL (PhotoGenica V-Star) and a 585-nm PDL (PhotoGenica V) at a pulse duration of 0.5 ms and a 10-mm handpiece. Treatment fluences were maintained below the individual's purpuric threshold, ranging from 3 to 4 J/cm2. Photos were taken before treatment and during follow-up. Efficacy of treatment was based on subjective grading of photos and by patient self-reporting. Results. Multiple treatments resulted in improvements to skin tone and texture, including a reduction in the appearance of rhytids and, in particular, improved pigmentary evenness. There was no significant difference between laser or treatment methods. No side effects were noted. Conclusion. PDL treatments provide effective photorejuvenation with minimal risk of side effects. [source] Treatment of Pigmented Hypertrophic Scars with the 585 nm Pulsed Dye Laser and the 532 nm Frequency-Doubled Nd:YAG Laser in the Q-Switched and Variable Pulse Modes: A Comparative StudyDERMATOLOGIC SURGERY, Issue 8 2002Leyda Elizabeth Bowes MD background. Pigmented hypertrophic scars are a difficult condition to treat. They may result from traumatic injuries or from surgical and cosmetic procedures. The 585 nm flashlamp-pumped pulsed dye laser (FLPDL) has been used to treat this condition, with significant improvement of varying degrees. It remains to be determined whether other laser modalities may have a similar or even greater success in the treatment of pigmented hypertrophic scars. objective. To determine the efficacy of the 532 nm frequency-doubled Nd:YAG laser in the treatment of pigmented hypertrophic scars as compared to the 585 nm FLPDL. methods. Six patients with pigmented hypertrophic scars and skin phototypes II,IV were chosen. A scar was selected for treatment in each patient and divided into four equal 2 cm segments. Three segments were each treated with a different laser modality and one was left untreated to serve as the control. A 585 nm FLPDL was used with an energy of 3.5 J, a pulse duration of 450 ,sec, and a 10 mm spot size. A 532 nm Q-switched frequency-doubled Nd:YAG laser was set to an energy of 2.8 J, a 10-nsec pulse, and a 3 mm spot size. The same 532 nm laser was set to the variable pulse mode to treat a 2 cm scar segment, with an energy of 9.5 J, a 10-msec pulse, and a 4 mm spot size. An average of 3.3 treatments were performed on each scar segment, at intervals of 4,6 weeks and long-term follow-up at 22 weeks. Treatment outcome was graded by a blind observer using the Vancouver General Hospital (VGH) Burn Scar Assessment Scale. A SigmaStat t -test was used to determine the statistical significance of the values obtained. results. Treatment of pigmented hypertrophic scars with the 532 nm Q-switched Nd:YAG laser led to a significant improvement of 38% in the VGH scores when compared to baseline (P = .005). The 585 nm FLPDL also had a favorable effect on the scars, with an average improvement of 36.1% in the VGH scores. There was no significant difference noted between the outcome of treatment with either of these two lasers. Treatment with the 532 nm variable pulse Nd:YAG laser led to a 19% improvement in the VGH scores of scars, which did not differ significantly from the 16.1% improvement observed in control scars on the last follow-up visit. No side effects or complications from treatment were noted or reported during the course of the study. At the conclusion of the study, five of six patients chose the segment treated with the 532 nm Q-switched Nd:YAG laser as the best segment overall. conclusion. The 532 nm Q-switched Nd:YAG laser and the 585 nm FLPDL offer comparable favorable results in the treatment of pigmented hypertrophic scars. The 532 nm Q-switched Nd:YAG laser may be preferred by patients particularly distressed by the dark color of their scars. [source] Minocycline-Induced Hyperpigmentation of the Tongue: Successful Treatment with the Q-Switched Ruby LaserDERMATOLOGIC SURGERY, Issue 3 2002Ilyse S. Friedman MD background. Minocycline-induced hyperpigmentation (MIH) is a benign condition that may persist for years despite abrogation of therapy. The Q-switched ruby laser (QSRL) has been successful in removing such lesions from the skin. To date there is no documentation of QSRL or any laser being used to treat lingual hyperpigmentation associated with minocycline therapy. objective. Long-term follow-up results are reported for the use of QSRL to treat lingual hyperpigmentation. The literature is reviewed comparing the use of different laser systems on MIH. methods. A 26-year-old woman with pigment changes of the tongue and buccal mucosa due to long-term minocycline therapy was treated with four consecutive sessions with QSRL (694 nm, 20-nsec pulse duration, and 6.5 mm spot size) at 3.6,4.0 J/cm2. results. A 90% resolution was achieved after three treatments. After the final treatment the lesions were completely gone. There were no side effects reported. No new pigment was detected at follow-up. conclusion. Treatment with the QSRL is a safe and effective strategy for treating hyperpigmentation of the tongue associated with minocycline therapy. [source] Laser Hair Removal: Long-Term Results with a 755 nm Alexandrite LaserDERMATOLOGIC SURGERY, Issue 11 2001Sorin Eremia MD Background. Hypertrichosis is a common problem for which laser hair removal is becoming the treatment of choice. Optimal wavelength, pulse duration, spot size, fluence, and skin cooling parameters for various skin types have not yet been firmly established. Objective. To evaluate the long-term efficacy and safety of a 3-msec 755 nm alexandrite laser equipped with a cryogen cooling device for patients with Fitzpatrick skin types I,V. Methods. Eighty-nine untanned patients with skin types I,V underwent a total of 492 treatments of laser hair removal over a 15-month period. Each patient in the study underwent a minimum of three treatment sessions spaced 4,6 weeks apart (mean treatments 5.6). Retrospective chart review and patient interviews were used to establish hair reduction results. Treatment sites included the axillae, bikini, extremities, face, and trunk. A 3-msec pulse width, 755 nm alexandrite laser equipped with a cryogen spray cooling device was used in this study. Spot sizes of 10,15 mm were used. A spot size of 10 mm was used for fluences greater than 40 J/cm2, a spot size of 12 mm was used for fluences of 35,40 J/cm2, and spot sizes of 12 and 15 mm were used for fluences less than 30 J/cm2. Fluences ranging from 20 to 50 J/cm2 (mean fluence 36 J/cm2) were used. Results. The patients had a mean 74% hair reduction. Skin type I patients had an average of 78.5% hair reduction using a mean fluence of 40 J/cm2 (35,50 J/cm2) and a 10,12 mm spot size (12 mm in more than 95% of treatments). Skin type II patients had a mean 74.3% hair reduction using a mean fluence of 38 J/cm2 (30,40 J/cm2) and a 12,15 mm spot size. Skin type III patients had a mean 73.4% hair reduction using a mean fluence of 37 J/cm2 (25,40 J/cm2) and a 12,15 mm spot size. Skin type IV patients had a mean 71.0% hair reduction using a mean fluence of 31 J/cm2 (25,35 J/cm2) and a 12,15 mm spot size. A patient with skin type V had a 60% hair reduction using a mean fluence of 23 J/cm2 (20,25 J/cm2) and a 12,15 mm spot size. The efficiency of hair removal directly correlates significantly with the fluence used. Rare side effects included transient postinflammatory hyperpigmentation (n = 9; 10%), burn with blisters (n = 1; 1%), and postinflammatory hypopigmentation (n = 2; 2%). All complications resolved without permanent scarring. Conclusion. The 3-msec cryogen cooling-equipped alexandrite laser can safely and effectively achieve long-term hair removal in patients with skin types I,V. The best results are achieved in untanned patients with skin types I,IV. [source] The Effects of Variable Pulse Width of Er:YAG Laser on Facial SkinDERMATOLOGIC SURGERY, Issue 4 2001Khalil A. Khatri MD Background. The use of CO2 and Er:YAG lasers for resurfacing has increased significantly in the past few years. Er:YAG laser causes pinpoint bleeding during and after treatment with a typical pulse width of 250 ,sec. A longer pulse of Er:YAG laser can potentially coagulate dermal blood vessels and increase the residual thermal damage (RTD). Objective. To evaluate the effects of various pulse durations of Er:YAG laser on the depth of RTD and bleeding. Methods. The preauricular skin of a volunteer was exposed to Er:YAG laser at 250-, 350-, and 700-,sec pulse durations, with a fluence of 5 J/cm2. The number of passes varied between 6 and 16. The treated skin was excised and a histologic evaluation was done. Results. The maximum depth of RTD was 50 ,m and there was decreased bleeding with a 700-,sec pulse duration. Conclusion. The increased pulse duration of Er:YAG laser of 700 ,s does not increase the maximum reported RTD and therefore would not change the recovery time and may have a beneficial effect on hemostasis. [source] Resurfacing of Pitted Facial Acne Scars with a Long-Pulsed Er:YAG LaserDERMATOLOGIC SURGERY, Issue 2 2001Jeung-Tae Jeong MD Background. Conventional short-pulsed Er:YAG lasers show less effective hemostasis and weak photothermal damage on papillary dermis. Recently, newer long-pulsed Er:YAG laser systems has been developed. Objective. To evaluate the clinical and histologic effects of long-pulsed Er:YAG laser resurfacing for pitted facial acne scars. Methods. Thirty-five patients with pitted facial acne scars were treated with a long-pulsed Er:YAG laser. All patients had Fitzpatrick skin phototypes III,V. A pulsed Er:YAG laser with a 5 mm handpiece at a setting of 7.0,7.5 J/cm2 with a 10-msec pulse duration was used. The laser was fired at 5 Hz, with four to five passes. In 28 patients, the results of laser treatment were evaluated for the degree of clinical improvement, duration of erythema, pigmentary change, and any adverse events at 2 weeks, 1 month, and 3 months. In seven patients, skin biopsy specimens were obtained at the following intervals: immediately, 1 week, 2 weeks, 4 weeks, and 8 weeks postoperatively for histologic examination. Results. The results of long-pulsed Er:YAG laser resurfacing for pitted facial acne scars were excellent in 10 patients (36%), good in 16 patients (57%), and fair in 2 patients (7%). Erythema occurred in all patients after laser treatment and lasted longer than 3 months in 15 patients (54%). Postinflammatory hyperpigmentation occurred in 8 patients (29%). But the pigmentation faded or disappeared within 3 months. One patient (4%) experienced mild hypopigmentation. Pruritic symptoms that required medical intervention occurred in 16 patients (57%). Mild to moderate postoperative acne flare-up occurred in 8 patients (29%). No other adverse effects such as scarring, bacterial infection, or contact dermatitis were observed. Conclusion. In conclusion, resurfacing with a long-pulsed Er:YAG laser is a safe and very effective treatment modality for pitted facial acne scars. [source] Androgen modulates the kinetics of the delayed rectifying K+ current in the electric organ of a weakly electric fishDEVELOPMENTAL NEUROBIOLOGY, Issue 12 2007M. Lynne McAnelly Abstract Weakly electric fish such as Sternopygus macrurus utilize a unique signal production system, the electric organ (EO), to navigate within their environment and to communicate with conspecifics. The electric organ discharge (EOD) generated by the Sternopygus electric organ is quasi-sinusoidal and sexually dimorphic; sexually mature males produce long duration EOD pulses at low frequencies, whereas mature females produce short duration EOD pulses at high frequencies. EOD frequency is set by a medullary pacemaker nucleus, while EOD pulse duration is determined by the kinetics of Na+ and K+ currents in the electric organ. The inactivation of the Na+ current and the activation of the delayed rectifying K+ current of the electric organ covary with EOD frequency such that the kinetics of both currents are faster in fish with high (female) EOD frequency than those with low (male) EOD frequencies. Dihydrotestosterone (DHT) implants masculinize the EOD centrally by decreasing frequency at the pacemaker nucleus (PMN). DHT also acts at the electric organ, broadening the EO pulse, which is at least partly due to a slowing of the inactivation kinetics of the Na+ current. Here, we show that chronic DHT treatment also slows the activation and deactivation kinetics of the electric organ's delayed rectifying K+ current. Thus, androgens coregulate the time-varying kinetics of two distinct ion currents in the EO to shape a sexually dimorphic communication signal. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007 [source] Complete Elucidation of Electrode Reaction Mechanisms by Using Differential Pulse PolarographyELECTROANALYSIS, Issue 17-18 2010Miguel, Rodríguez Mellado Abstract By exploring the different parameters of the technique, it is shown that Differential Pulse Polarography (DPP) can be used for the elucidation of the reaction mechanisms of the electrochemical processes (with the evident exception of the product and intermediate identification). So, the type of transport towards or from the electrode can be identified from the dependence of the intensities with the pulse amplitude, the electrochemical reaction order with respect to the electroactive species from the shape of the polarogram, the type of rate-determining step from the dependence of the peak potentials on the pulse duration, the electrochemical reaction order with respect to other species, such as the H+ion, from the dependence of the peak potentials on their concentrations etc. [source] Female Mate Choice, Calling Song and Genetic Variance in the Cricket, Gryllodes sigillatusETHOLOGY, Issue 3 2008Jocelyn Champagnon Female preferences for song patterns of males of Gryllodes sigillatus and genetic variance of morphological traits correlated with them were analyzed. Females preferred short pulses associated with large males. The males' thorax width, wing length and femur III length showed stronger relationship with the song pulse duration, whereas the relationship between pulse duration and wing width was not significant. Interestingly, this last trait was the only one that showed significant levels of genetic variance. Perhaps these results could be explained by the evolutionary response to sexual selection. Sexual selection could deplete the genetic variance in the male traits related to male-mating success. [source] Ontogeny of Acoustic and Feeding Behaviour in the Grey Gurnard, Eutrigla gurnardusETHOLOGY, Issue 3 2005M. Clara P. Amorim Although sound production in teleost fish is often associated with territorial behaviour, little is known of fish acoustic behaviour in other agonistic contexts such as competitive feeding and how it changes during ontogeny. The grey gurnard, Eutrigla gurnardus, frequently emits knock and grunt sounds during competitive feeding and seems to adopt both contest and scramble tactics under defensible resource conditions. Here we examine, for the first time, the effect of fish size on sound production and agonistic behaviour during competitive feeding. We have made sound (alone) and video (synchronized image and sound) recordings of grey gurnards during competitive feeding interactions. Experimental fish ranged from small juveniles to large adults and were grouped in four size classes: 10,15, 15,20, 25,30 and 30,40 cm in total length. We show that, in this species, both sound production and feeding behaviour change with fish size. Sound production rate decreased in larger fish. Sound duration, pulse duration and the number of pulses increased whereas the peak frequency decreased with fish size, in both sound types (knocks and grunts). Interaction rate and the frequency of agonistic behaviour decreased with increasing fish size during competitive feeding sessions. The proportion of feeding interactions accompanied by sound production was similar in all size classes. However, the proportion of interactions accompanied by knocks (less aggressive sounds) and by grunts (more aggressive) increased and decreased with fish size, respectively. Taken together, these results suggest that smaller grey gurnards compete for food by contest tactics whereas larger specimens predominantly scramble for food, probably because body size gives an advantage in locating, capturing and handling prey. We further suggest that sounds emitted during feeding may potentially give information on the motivation and ability of the individual to compete for food resources. [source] Laser-induced breakdown spectroscopy for soil diagnosticsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2001J. Bublitz Summary Laser-optical measurements and fibre optics are potentially attractive tools for applications in soil science because of their great sensitivity and selectivity and their capabilities for on-line and in situ analysis. We have investigated laser-induced breakdown spectroscopy (LIBS) for the quantitative detection of metal ions on the surface of natural soil samples from two sites (Hohenschulen and Oderbruch, Germany). The LIBS technique allows the spatially resolved investigation of adsorption and desorption effects of ions in soil. A frequency doubled (532 nm) and Q-switched Nd:YAG laser with a pulse duration of 8 ns is focused on the soil surface and induces a plasma. Typical power densities are 150 mJ mm,2. The plasma emission is recorded in time and spectrally resolved by a gateable optical multichannel analyser (OMA). A delay time of about 500 ns between laser pulse and OMA gate was used to resolve single atomic and ionic spectral lines from the intense and spectrally broad light that is emitted by the plasma itself. The dependency of the LIBS signal of a single spectral line on the amount of water in the sample is investigated in detail. The results indicate that quenching of water in the plasma plume reduces the line intensities, while the interaction with aquatic colloids increases the intensity. The two processes compete with each other, and a non-linear correlation between measured line intensities and the amount of water in the sample is obtained. This is verified by a simple computer simulation and has to be taken into account for the quantitative interpretation of LIBS signals, e.g. when absolute concentrations are estimated. In the present investigation natural calcium concentrations <,2 ,g kg,1 were measured with the LIBS technique in the samples for the two test sites. In addition, measurements were made with dry and water-saturated BaCl2 mixed soil samples, and no significant difference in the detection limit for barium was obtained. [source] ADVERTISEMENT-CALL PREFERENCES IN DIPLOID-TETRAPLOID TREEFROGS (HYLA CHRYSOSCELIS AND HYLA VERSICOLOR): IMPLICATIONS FOR MATE CHOICE AND THE EVOLUTION OF COMMUNICATION SYSTEMSEVOLUTION, Issue 2 2005H. Carl Gerhardt Abstract Signals used for mate choice and receiver preferences are often assumed to coevolve in a lock-step fashion. However, sender-receiver coevolution can also be nonparallel: even if species differences in signals are mainly quantitative, females of some closely related species have qualitatively different preferences and underlying mechanisms. T o-alternative playback experiments using synthetic calls that differed in fine-scale temporal properties identified the receiver criteria in females of the treefrog Hyla chrysoscelis for comparison with female criteria in a cryptic tetraploid species (H. versicolor); detailed preference functions were also generated for both species based on natural patterns of variation in temporal properties. The species were similar in three respects: (1) pulses of constant frequency were as attractive as the frequency-modulated pulses typical of conspecific calls; (2) changes in preferences with temperature paralleled temperature-dependent changes in male calls; and (3) preference functions were unimodal, with weakly defined peaks estimated at values slightly higher than the estimated means in conspecific calls. There were also species differences: (1) preference function slopes were steeper in H. chrysoscelis than in H. versicolor; (2) preferences were more intensity independent in H. chrysoscelis than in H. versicolor; (3) a synergistic effect of differences in pulse rate and shape on preference strength occurred in H. versicolor but not in H. chrysoscelis; and (4) a preference for the pulse shape typical of conspecific calls was expressed at the species-typical pulse duration in H. versicolor but not in H. chrysoscelis. However, females of H. chrysoscelis did express a preference based on pulse shape when tested with longer-than-average pulses, suggesting a hypothesis that could account for some examples of nonparallel coevolution. Namely, preferences can be hidden or revealed depending on the direction of quantitative change in a signal property relative to the threshold for resolving differences in that property. The results of the experiments reported here also predict patterns of mate choice within and between contemporary populations. First, intraspecific mate choice in both species is expected to be strongly influenced by variation in temperature among calling males. Second, simultaneous differences in pulse rate and pulse shape are required for effective species discrimination by females of H. versicolor but not by females of H. chrysoscelis. Third, there is greater potential for sexual selection within populations and for discrimination against calls produced by males in other geographically remote populations in H. chrysoscelis than in H. versicolor. [source] Hair removal using an 800-nm Diode Laser: Comparison at different treatment intervals of 45, 60, and 90 daysINTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 1 2005Navid Bouzari MD Background, Some laser irradiation parameters such as wavelength, fluence, pulse duration, and spot size have been shown to influence the damage of any target inside the skin, however, the role of some patients' factors such as hair growth cycle is still under debate. Objective, To determine the association of treatment interval and laser treatment outcome. Methods, In a retrospective chart review of 176 patients undergoing laser-assisted hair removal with a diode laser 24 patients were selected. All accepted to cease the therapy, and be followed-up for 5 months. At the end of the study the patients were questioned about the efficacy of the treatment as well as the adverse effects. Hair counting was also performed. The adverse effects (pain, blister or erosion, hyperpigmentation, hypopigmentation, and folliculitis) were questioned during the follow-up period. Results, The mean hair reduction was 78.1%, 45.8%, and 28.7% in 45, 60, and 90-day interval groups, respectively (P < 0.0001). Conclusion, The treatment interval was related to the treatment outcome in our study. [source] Root surface roughness following Er:YAG laser irradiation at different radiation energies and working tip angulationsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 7 2002Matthias Folwaczny Abstract Objectives: The determination of roughness of root surfaces following treatment with 2.94 µm Er:YAG laser radiation at different radiation energies and working tip angulations. Materials and methods: The study sample comprised 85 extracted human molars, premolars, canines and incisors (n = 85). The source of laser radiation was an Er:YAG laser device (KAVO-Key II, System Aesculap Meditec) emitting pulsed infrared radiation at a wavelength of 2.94 µm, with a pulse duration of 250 µs, and a pulse repetition rate of 10 pps. The samples were randomly divided into three experimental units, for treatment with a constant amount of 380 laser pulses at a radiation energy of 60 mJ, 100 mJ, and 180 mJ. Each experimental unit was divided into five subgroups of five samples, which were irradiated at a working tip angulations of 15°, 30°, 45°, 60°, and 90°. Five samples were treated mechanically using curettes. Five samples were left untreated as control. The mean (Ra) and maximum (Rmax) surface roughness of each sample was measured using a profilometer. The statistical analysis was undertaken using anova and Scheffé-test at a level of significance of 5% (p < 0.05). Results: Er:YAG laser radiation led to an Ra which ranged from 0.52 µm (± 0.10) to 0.81 µm (± 0.26) and to an Rmax between 3.4 µm (± 0.48) and 9.26 µm (± 3.08). The Ra and Rmax for samples treated with curettes was 0.51 µm (± 0.11) and 5.08 µm (± 4.98), respectively. That for the untreated control samples were 0.53 µm (± 0.15) and 7.07 µm (± 5.48), respectively. Conclusions: The mean and maximum surface roughness of root surfaces following irradiation with Er:YAG laser was not significantly different to that obtained on samples treated with conventional hand instruments or left untreated. Furthermore, the surface roughness does not depend on the radiation energy and the angulation of the working tip. [source] Scale effects and constraints for sound production in katydids (Orthoptera: Tettigoniidae): correlated evolution between morphology and signal parametersJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2009F. MONTEALEGRE-Z Abstract Male katydids (Orthoptera: Tettigoniidae) produce mating calls by rubbing the wings together, using specialized structures in their forewings (stridulatory file, scraper and mirror). A large proportion of species (ca. 66%) reported in the literature produces ultrasonic signals as principal output. Relationships among body size, generator structures and the acoustic parameters carrier frequency (fc) and pulse duration (pd), were studied in 58 tropical species that use pure-tone signals. A comparative analysis, based on the only available katydid phylogeny, shows how changes in sound generator form are related to changes in fc and pd. Anatomical changes of the sound generator that might have been selected via fc and pd are mirror size, file length and number of file teeth. Selection for structures of the stridulatory apparatus that enhance wing mechanics via file-teeth and scraper morphology was crucial in the evolution of ultrasonic signals in the family Tettigoniidae. [source] EFFECTS of PULSED ELECTRIC FIELD ON QUALITY FACTORS and MASS TRANSFER DURING OSMOTIC DEHYDRATION of APPLESJOURNAL OF FOOD PROCESS ENGINEERING, Issue 1 2003KEHINDE A. TAIWO ABSTRACT High intensity electric field pulses using varying field strengths (0.5, 1.0 and 2.0 kV/cm corresponding to 12, 48 and 192 J/kg, per pulse, respectively, with a pulse duration of 400,s) and pulse numbers (2 to 50) were applied to apple slices as a pretreatment to study their influence on mass transfer during osmotic dehydration (OD). Cell membrane permeabilzation increased with increasing field strength and higher pulse number. Higher water loss and solids gain were obtained at 1.0 kV/cm. Pretreated apples turned brown but sample brightness improved with OD time but L values decreased with increasing pulse number. Maximum deformative force and amount of strain experienced by dried samples were influenced by both the field strength and OD time. Vitamin C content of dried samples reduced at higher field strengths and longer immersion times. [source] Stimulation threshold comparison of time-varying magnetic pulses with different waveformsJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2009Werner Irnich PhD Abstract Purpose To clarify whether sinusoidal pulses possess lower thresholds than rectangular ones at perception threshold, a statement often made that contradicts the theory of stimulation. Materials and Methods The results of a nerve stimulation study with 65 volunteers and with trapezoidal and sinusoidal gradient pulses were used to apply the combination of the electric field, induced in the tissue of the human body, with the "Fundamental Law of Electrostimulation." This law claims that the waveshape of a pulse is not essential as long as the amplitude of the pulse does not decrease below rheobase (rheobase condition). Results If the rheobase condition is applied to sinusoidal waveforms and the pulse duration and amplitude is corrected accordingly, both trapezoidal and sinusoidal gradient pulses have identical threshold amplitudes as a function of pulse duration. Conclusion The "Fundamental Law of Electrostimulation," including the "rheobase condition," proved to be a good basis for describing magnetic field stimulation (magnetostimulation) and that application of it to magnetostimulation is suitable as the basis for describing magnetic field stimulation with various waveforms. For nonrectangular pulses, pulse durations and pulse amplitudes must be corrected according to the "rheobase condition." The exponential Blair Equation is less suited to be applied in magnetostimulation. J. Magn. Reson. Imaging 2009;29:229,236. © 2008 Wiley-Liss, Inc. [source] A2A Adenosine Receptor Facilitation of Neuromuscular TransmissionJOURNAL OF NEUROCHEMISTRY, Issue 6 2000Influence of Stimulus Paradigm on Calcium Mobilization Abstract: The influence of stimulus pulse duration on calcium mobilization triggering facilitation of evoked [3H]acetylcholine ([3H]ACh) release by the A2A adenosine receptor agonist CGS 21680C was studied in the rat phrenic nerve-hemidiaphragm. The P-type calcium channel blocker ,-agatoxin IVA (100 nM) decreased [3H]ACh release evoked with pulses of 0.04-ms duration, whereas nifedipine (1 ,M) inhibited transmitter release with pulses of 1-ms duration. Depletion of intracellular calcium stores by thapsigargin (2 ,M) decreased [3H]ACh release evoked by pulses of 1 ms, an effect observed even in the absence of extracellular calcium. With short (0.04-ms) stimulation pulses, when P-type calcium influx triggered transmitter release, facilitation of [3H]ACh release by CGS 21680C (3 nM) was attenuated by both thapsigargin (2 ,M) and nifedipine (1 ,M). With longer stimuli (1 ms), a situation in which both thapsigargin-sensitive internal stores and L-type channels are involved in ACh release, pretreatment with either ,-agatoxin IVA (100 nM) or nifedipine (1 ,M) reduced the facilitatory effect of CGS 21680C (3 nM). The results suggest that A2A receptor activation facilitates ACh release from motor nerve endings through alternatively mobilizing the available calcium pools (thapsigargin-sensitive internal stores and/or P- or L-type channels) that are not committed to the release process in each stimulation condition. [source] NOx storage and reduction with propylene on Pt/BaO/aluminaAICHE JOURNAL, Issue 10 2004Rachel L. Muncrief Abstract An experimental study was carried out of periodically operated NOx (NO + NO2) storage and reduction on a model Pt/BaO/Al2O3 catalyst powder. The effect of the reductant (propylene) injection policy on time-averaged NOx conversion was evaluated in terms of feed composition and temperature, reductant pulse duration, and overall cycle time. Conditions giving time-averaged NOx conversions exceeding 90% were identified. The reductant-to-oxidant ratio during the injection and the total cycle time are both found to be critical factors to achieve high conversion. The time-averaged conversion is bounded above and below by the steady-state conversions obtained with feeds having the same compositions as that during the rich and lean part of the cycle, respectively. For a fixed supply of propylene, short pulses of high concentration are much more effective than longer pulses of reduced concentration. The NOx conversion achieves a maximum value at an intermediate overall cycle time when the propylene pulse of fixed duty fraction is net reducing. High conversions are sustained over a wide temperature window (200,400°C). A simple storage,reduction cycle is proposed that elucidates the main findings in the study. The key factor for high NOx conversion is the temporal production of oxygen-deficient conditions coupled with high catalyst temperatures, both resulting from the intermittent catalytic oxidation of propylene. © 2004 American Institute of Chemical Engineers AIChE J, 50: 2526,2540, 2004 [source] Over 8 W high peak power UV laser with a high power Q-switched Nd:YVO4 oscillator and the compact extra-cavity sum-frequency mixingLASER PHYSICS LETTERS, Issue 2 2009X.P. Yan Abstract A 8.2 W UV laser was reported with the compact extra-cavity sum-frequency mixing. The IR fundamental frequency source was a high power and high beam quality Q-switched Nd:YVO4 oscillator. 38Wfundamental frequency laser at 1064 nm was obtained at the pulse repetition rate of 450 kHz with the beam quality factors of M2x = 1.27, M2y = 1.21. The type I and type II phase-matched LBO crystals were used as the extra-cavity frequency doubling and mixing crystals respectively. At 38 kHz, 8.2 W UV laser at 355 nm was achieved with the pulse duration of 8 ns corresponding to the pulse peak power as high as 27 kW, and the optical-optical conversion efficiency from IR to UV was 25.6%. The output characteristics of the IR and the harmonic generations varying with the pulse repetition rate were also investigated detailedly. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Dynamic resonances in ultra-short laser pulsesLASER PHYSICS LETTERS, Issue 6 2007N.V. Bordyug Abstract Dynamic multiphoton resonances in ultra-short superintense laser pulses consisting of 50,200 field periods are considered numerically for a two-level system. The impact of nonresonant (Bloch-Siegert) and carrier-envelope effects on the dynamics of a two-level system was studied numerically, and conditions for complete population inversion were derived. The widths of multiphoton resonances increase with the increasing of the laser field. Results do not depend practically on the pulse duration. Effective resonance frequencies for multiphoton resonances increases strongly in a super-intense field. Multiphoton resonances are shifted and unified with each other in super-intense laser fields. (© 2007 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Bidirectional operation and gyroscopic properties of passively mode-locked Nd:YVO4 ring laserLASER PHYSICS LETTERS, Issue 3 2007Y. Liu Abstract A simple LD-end-pumped, passively mode-locked Nd:YVO4 ring laser with bidirectional outputs was demonstrated, and the gyroscopic properties of the ring laser was studied. The laser was continuous wave mode-locked by use of a semiconductor saturable absorber mirror (SESAM), and both clockwise and counter-clockwise outputs are stable laser pulse trains with pulse duration of 64 ps. The continuous wave modelocking was obtained under pump power as low as 540 mW. The average output power is 50 mW for the counter-clockwise laser and 52 mW for the clockwise laser under pump power of 1378 mW. The whole slope efficiency of the ring laser is about 9.4%. The two output pulse trains of the ring laser were combined to study its gyroscopic properties. The beat frequency of the pulsed solid-state laser gyro versus the rotation rates follows the Sagnac formula. The laser gyro has a large dead band of 6 , 8 dec/s, which was believed to be caused by the long pulse duration and the colliding of the opposite pulses on the SESAM. (© 2007 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) (© 2007 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Intense pulsed light (IPL): A reviewLASERS IN SURGERY AND MEDICINE, Issue 2 2010Philipp Babilas MD Abstract Background Intense pulsed light (IPL) devices use flashlamps and bandpass filters to emit polychromatic incoherent high-intensity pulsed light of determined wavelength spectrum, fluence, and pulse duration. Similar to lasers, the basic principle of IPL devices is a more or less selective thermal damage of the target. The combination of prescribed wavelengths, fluences, pulse durations, and pulse intervals facilitates the treatment of a wide spectrum of skin conditions. Objective To summarize the physics of IPL, to provide guidance for the practical use of IPL devices, and to discuss the current literature on IPL in the treatment of unwanted hair growth, vascular lesions, pigmented lesions, acne vulgaris, and photodamaged skin and as a light source for PDT and skin rejuvenation. Methods A systematic search of several electronic databases, including Medline and PubMed and the authors experience on intense pulsed light. Results Numerous trials show the effectiveness and compatibility of IPL devices. Conclusion Most comparative trials attest IPLs similar effectiveness to lasers (level of evidence: 2b to 4, depending on the indication). However, large controlled and blinded comparative trials with an extended follow-up period are necessary. Lasers Surg. Med. 42:93,104, 2010. © 2009 Wiley-Liss, Inc. [source] Pulpal effects of enamel ablation with a microsecond pulsed ,,=,9.3-µm CO2 laserLASERS IN SURGERY AND MEDICINE, Issue 4 2009Michal Staninec DDS Abstract Background and Objectives In vitro studies have shown that CO2 lasers operating at the highly absorbed 9.3 and 9.6-µm wavelengths with a pulse duration in the range of 10,20-microsecond are well suited for the efficient ablation of enamel and dentin with minimal peripheral thermal damage. Even though these CO2 lasers are highly promising, they have yet to receive FDA approval. Clinical studies are necessary to determine if excessive heat deposition in the tooth may have any detrimental pulpal effects, particularly at higher ablative fluencies. The purpose of this study was to evaluate the pulpal safety of laser irradiation of tooth occlusal surfaces under the conditions required for small conservative preparations confined to enamel. Study Design/Materials and Methods Test subjects requiring removal of third molar teeth were recruited and teeth scheduled for extraction were irradiated using a pulsed CO2 laser at a wavelength of 9.3 µm operating at 25 or 50 Hz using a incident fluence of 20 J/cm2 for a total of 3,000 laser pulses (36 J) for both rates with water cooling. Two control groups were used, one with no treatment and one with a small cut made with a conventional high-speed hand-piece. No anesthetic was used for any of the procedures and tooth vitality was evaluated prior to treatment by heat, cold and electrical testing. Short term effects were observed on teeth extracted within 72 hours after treatment and long term effects were observed on teeth extracted 90 days after treatment. The pulps of the teeth were fixed with formalin immediately after extraction and subjected to histological examination. Additionally, micro-thermocouple measurements were used to estimate the potential temperature rise in the pulp chamber of extracted teeth employing the same irradiation conditions used in vivo. Results Pulpal thermocouple measurements showed the internal temperature rise in the tooth was within safe limits, 3.3±1.4°C without water cooling versus 1.7±1.6°C with water-cooling, n,=,25, P<0.05. None of the control or treatment groups showed any deleterious effects on pulpal tissues and none of the 29 test-subjects felt pain or discomfort after the procedure. Only two test-subjects felt discomfort from "cold sensitivity" during the procedure caused by the water-spray. Conclusion It appears that this CO2 laser can ablate enamel safely without harming the pulp under the rate of energy deposition employed in this study. Lasers Surg. Med. 41:256,263, 2009. © 2009 Wiley-Liss, Inc. [source] | ||||||||||||||||||||||||||||||||||||||||