Extrapolation Of Curve Research Articles

Different sampling intervals for bowl trapping survey of Aculeata (Hymenoptera) in a semidecidual seasonal forest fragment

Coloured bowl trapping is a passive sampling method which catches insects through a combination of interception and attraction. The method is commonly used for Aculeata, especially bees. The objective of the present study is to determine a reliable sampling interval for aculeates using bowl traps since an appropriate sampling interval is important to enable the collection of representative samples in Neotropics. For this purpose we installed eight bowl traps in a forest fragment in Southern Brazil, during one year, to compare the sampled diversity in twice and once-a-month sampling interval. We confirmed the general expectation that increasing the sample size results in a proportional greater sampling of the community. Different sampling intervals have a weak impact in rarefaction curves, as these do not reach the asymptote in any cases, and Shannon diversity index was considered statistically equal. Under our results, the twice-a-month interval was considered better than monthly sampling intervals only when we compare the extrapolation data (estimators and extrapolation curve) for Aculeata. The Shannon diversity index and the estimated species number (rarefaction) were considered the same among the treatments, so we cannot suggest a reliable sampling interval from these data.

Extrapolation of Imaginal Minimum Creep Rate in Compression by a Concept of SATO-Index

Creep characteristics of alloys and compounds have been evaluated mainly by the minimum creep rate or the steady-state creep rate, and by its stress and temperature dependences. In some cases, however, direct comparison of the minimum creep rate or the steady-state creep rate are not practically easy due to difficulties of experiment, i.e., a long duration of primary stage of creep deformation. The minimum creep rates are not always precise representative value, which is directly evaluated from experiments. It should be valuable, if one could estimate the minimum creep rate from creep curve in primary stage. I have proposed a method of quantitative evaluation of creep curve based on the evaluation of strain rate change and its strain dependence during creep [1-3]. The value that reflects a shape of creep curve is named “Strain Acceleration and Transition Objective-Index (SATO-Index)” [4]. SATO-Index and related differential equation show a strain dependence of strain rate and lead entre creep curve by numerical integration. This concept provides quantitative information of shape of each creep curve, and information of the entire creep curve. In this paper, examples of evaluation and extrapolation of creep rate from primary stage in compression are presented. It is concluded that the extrapolation with the concept of SATO-Index reasonably provides imaginal minimum creep rate. Usability of extrapolation of creep curve by the concept is presented.

Minimally invasive estimation of ventricular dead space volume through use of Frank-Starling curves.

This paper develops a means of more easily and less invasively estimating ventricular dead space volume (Vd), an important, but difficult to measure physiological parameter. Vd represents a subject and condition dependent portion of measured ventricular volume that is not actively participating in ventricular function. It is employed in models based on the time varying elastance concept, which see widespread use in haemodynamic studies, and may have direct diagnostic use. The proposed method involves linear extrapolation of a Frank-Starling curve (stroke volume vs end-diastolic volume) and its end-systolic equivalent (stroke volume vs end-systolic volume), developed across normal clinical procedures such as recruitment manoeuvres, to their point of intersection with the y-axis (where stroke volume is 0) to determine Vd. To demonstrate the broad applicability of the method, it was validated across a cohort of six sedated and anaesthetised male Pietrain pigs, encompassing a variety of cardiac states from healthy baseline behaviour to circulatory failure due to septic shock induced by endotoxin infusion. Linear extrapolation of the curves was supported by strong linear correlation coefficients of R = 0.78 and R = 0.80 average for pre- and post- endotoxin infusion respectively, as well as good agreement between the two linearly extrapolated y-intercepts (Vd) for each subject (no more than 7.8% variation). Method validity was further supported by the physiologically reasonable Vd values produced, equivalent to 44.3–53.1% and 49.3–82.6% of baseline end-systolic volume before and after endotoxin infusion respectively. This method has the potential to allow Vd to be estimated without a particularly demanding, specialised protocol in an experimental environment. Further, due to the common use of both mechanical ventilation and recruitment manoeuvres in intensive care, this method, subject to the availability of multi-beat echocardiography, has the potential to allow for estimation of Vd in a clinical environment.

Total phenolic and tannins determination: a modification of Ph. Eur. 2.8.14 for higher throughput.

A principle mostly being used to quantify phenols and tannins is the Folin-Ciocalteu's reagent method described in the European Pharmacopeia's method 2.8.14. Aim of the present study was to simplify this procedure in order to handle larger sample numbers. By changing the wavelength, the amounts of reagents, miniaturizing the setting to microtiter scale and changing the incubation time before measurement, the Ph. Eur. method 2.8.14 was optimized for a larger number of experiments. Calibration curves and time kinetics with different phenolic compounds (catechol, procyanidin B1, gallic acid, (+)-catechin, tannic acid, salicylic acid, ferulic acid) were determined. In addition, the absorbance of a 1 M solution was calculated by extrapolation of each calibration curve, to examine correlations due to the reaction's stoichiometry. Furthermore, the repeatability concerning herbal samples was investigated using Quercus cortex. The method was validated concerning its repeatability, robustness, linearity and reproducibility. Using this method, at least 120 samples can be handled per day by one person to quantify the total phenolic and tannin content.

Current knowledge of fungi from Neotropical montane cloud forests: distributional patterns and composition

Montane cloud forests in the Neotropics harbor a great wealth of biological diversity and a large number of endemic species. Here, we present (i) a comprehensive data mining exercise of fungi from Neotropical montane cloud forests (NMCF), (ii) an extensive review of the current knowledge of fungal richness, distribution and composition, and (iii) a preliminary analysis of fungal endemicity in Mexican montane cloud forests. Based on a survey of literature and other sources, we assembled a database of 6349 records representing 2962 fungal species in NMCF. The computed individual-based species rarefaction curve remained non-asymptotic, and the extrapolation curve estimated an expected increment of 42% in the number of species by doubling the sampling effort. Fungal species richness was highest in NMCF from Mesoamerica, particularly from Mexico and Costa Rica. Fungi from Mesoamerica, Caribbean and South America are significantly different at diverse taxonomic levels, and there is a little overlap in the fungal species recorded from these regions. The analyses of endemicity of the Mexican dataset performed with parsimony and Bayesian methods were highly complementary. They showed the following areas of endemicity supported by the congruent distribution of fungal species: (i) two main regions in the Trans-Mexican Volcanic Belt (TMVB); (ii) a region in the southern part of Veracruz; and (iii) a region located in the eastern part of TMVB with affinities with Sierra Madre Oriental and the Chiapan-Guatemala Highlands. This last area was supported by five species of Glomeromycota and is consistent with an area of endemicity previously found in vascular plants. In this study, we provide a perspective on gaps in knowledge regarding the diversity and distribution of fungi in NMCF, and provide a full dataset of fungal records with geographical, bibliographic and taxonomic information.

Long-term prognostic impact of the Great East Japan Earthquake in patients with cardiovascular disease – Report from the CHART-2 Study

BackgroundWe and others have previously reported that the Great East Japan Earthquake (GEJE) caused a significant but transient increase in cardiovascular diseases and deaths in the disaster area. However, it remains to be examined whether the GEJE had a long-term prognostic influence in large-scale cohort studies. This point is important when analyzing the data before and after the GEJE in the cohort studies in the disaster area. MethodsWe examined 8676 patients registered in our Chronic Heart Failure Analysis and Registry in the Tohoku District-2 (CHART-2) Study (N=10,219) between 2006 and 2010 and were alive after March 10, 2011. ResultsThere were 48 GEJE-related deaths, causing a sharp and transient increase in all-cause death within a month after the GEJE. However, after excluding the GEJE-related deaths, the cubic polynomial spline smoothing showed no significant increase in all-cause death, heart failure admission, non-fetal acute myocardial infarction, or non-fetal stroke during the median 3-year follow-up after the GEJE. The extrapolation curves beyond the GEJE, which were obtained by the parametric survival models based on the survival data censored on the GEJE, were not significantly different from the Kaplan–Meier curves estimating the survival functions of deaths and cardiac events during the total follow-up period without considering the impacts of the GEJE. Furthermore, the multivariate Cox proportional hazard model applied to the matched cohort of the baseline data and the data after the GEJE showed no significant differences in the impacts of prognostic factors on all-cause mortality before and after the GEJE. ConclusionsThese results indicate that the GEJE had no significant long-term prognostic impact after the earthquake in cardiovascular patients in the disaster area.

Species richness and abundance of Saturniidae (Lepidoptera) in a tropical semi-deciduous forest of Veracruz, Mexico and the influence of climatic variables

The knowledge of saturniid moths is relevant because of their susceptibility to environmental conditions and the important number of ecological interactions they exhibit. In this study we report the species richness and abundance of the saturniids captured in a fragment of tropical semi-deciduous forest in central Veracruz, Mexico. The moths were attracted using 250W mercury vapor lamp 1 night per month from September 2014 to August 2015. Thirty-one species belonging to 18 genera, 2 tribes and 4 subfamilies were determined. The total number of species constitutes 6.87% and 30.39% of the species known from Mexico and Veracruz, respectively. Coverage-based rarefaction and an extrapolation curve showed high diversity compared with previous studies in Mexico. Antheraea polyphemus mexicana, Automeris montezuma, Citheronia lobesi jordani, Hylesia coinopus, Molippa ninfa, and Pseudodirphia mexicana are endemic from Mexico. The highest richness and abundance of species were observed in May with 77% of the species collected during this month. These variables are thought to extend periods of flight activity for copulations. This study provides a survey of Saturniidae family species richness and abundance in one of the most diverse, but disturbed ecosystems of Veracruz.

Assessment of 21st century drought conditions at Shasta Dam based on dynamically projected water supply conditions by a regional climate model coupled with a physically-based hydrology model.

Along with socioeconomic developments, and population increase, natural disasters around the world have recently increased the awareness of harmful impacts they cause. Among natural disasters, drought is of great interest to scientists due to the extraordinary diversity of their severity and duration. Motivated by the development of a potential approach to investigate future possible droughts in a probabilistic framework based on climate change projections, a methodology to consider thirteen future climate projections based on four emission scenarios to characterize droughts is presented. The proposed approach uses a regional climate model coupled with a physically-based hydrology model (Watershed Environmental Hydrology Hydro-Climate Model; WEHY-HCM) to generate thirteen equally likely future water supply projections. The water supply projections were compared to the current water demand for the detection of drought events and estimation of drought properties. The procedure was applied to Shasta Dam watershed to analyze drought conditions at the watershed outlet, Shasta Dam. The results suggest an increasing water scarcity at Shasta Dam with more severe and longer future drought events in some future scenarios. An important advantage of the proposed approach to the probabilistic analysis of future droughts is that it provides the drought properties of the 100-year and 200-year return periods without resorting to any extrapolation of the frequency curve.

Material characterization for plane and curved sheets using the in-plane torsion test – an overview

Abstract The in-plane torsion test offers a broad range of applications for the characterization of mechanical properties of sheet metal materials and components. True plastic strains up to 1.0 can be achieved. Such data can be used for the numerical analysis without extrapolation of the flow curve. The stress and strain state correspond to ideal simple shear during the entire process. The application range of the plane torsion test has been constantly expanded by different approaches and a more sophisticated evaluation has been developed. The full-field analysis of the test area makes it possible to determine an almost arbitrary number of cyclic flow curves with only one single specimen. By using a grooved specimen, the ideal simple shear state can be obtained until fracture of the material without inhomogeneities. New investigations show that the in-plane torsion test is also suitable for the determination of flow curves for curved surfaces. Investigations on curved rotationally symmetrical as well as a tubular shape were performed. Finally, first results for the local determination of the strength’ arbitrary locations of a component are presented.

Electrochemical corrosion of Al-Pd alloys in HCl and NaOH solutions

The corrosion performance of as-solidified Al-Pd alloys in HCl and NaOH aqueous solutions is investigated in this work. Four different alloys (Al88Pd12, Al77Pd23, Al72Pd28 and Al67Pd33, element concentrations are given in at.%) were prepared from high purity Al and Pd lumps by arc-melting in Ar. Subsequently, the alloy microstructure and phase occurrence were investigated by a combination of scanning electron microscopy and room-temperature powder X-ray diffraction. The assolidified Al-Pd alloys were found to consist of several single-phase microstructure constituents with various structures and chemical compositions, including structurally complex intermetallic phases. The polished surfaces of the Al-Pd alloys were subjected to electrochemical polarization in aqueous HCl and NaOH solutions (0.01 mol.dm-3) at 21?2?C. The corrosion experiments were conducted in a standard 3-electrode cell controlled by potentiostat. The corrosion potentials and corrosion current densities were determined by Tafel extrapolation of the experimental polarization curves. Phase dissolution has been observed on the alloy surfaces and some of the phases were preferentially corroded. The effects of the alloy microstructure and the phase occurrence are evaluated. The local nobility of individual intermetallic compounds is discussed. Finally, the conclusions for the alloys corrosion performance in acidic and basic solutions are provided.

Chemical Mechanical Planarization of Ruthenium Using Sodium Hypochlorite Based Titania Slurry

In the present work, chemical mechanical planarization (CMP) of Ru and Cu was carried out using titania based slurry containing sodium hypochlorite (NaOCl) as oxidizer with and without benzotriazole (BTA) as corrosion inhibitor. The CMP results reveal that in the absence of BTA, Ru removal rate (RR) increases with pH until pH 7 and then decreases gradually in the alkaline region, while Cu RR decreases with increase in pH. In the presence of BTA, both Cu and Ru removal rates decreased while the same trend in RR was observed with change in pH. RR selectivity between Ru and Cu of 1 was obtained at pH 9 which is preferred in industries. In the presence of NaOCl, Ru oxidizes to form RuO4, in the acidic and neutral pH and RuO4− and RuO42− in alkaline pH, which aids in the formation of RuO3/RuO2. The electrochemical techniques were also employed to understand the removal mechanism of Ru and Cu in electrolyte containing NaOCl with and without BTA. The Icorr values of Ru and Cu, obtained from the extrapolation of Tafel curves, follow the CMP removal rate trend. An electrical equivalent circuit was proposed to explain the results obtained in electrochemical impedance spectroscopy studies.

OP60 Ramucirumab In Gastric Cancer Treatment: An Economic Evaluation

INTRODUCTION:Gastric cancer (GC) is one of the most common malignancy and the third leading cause of cancer mortality worldwide. Currently, platinum-based and fluoropyrimidine-based combinations represent the milestone of front-line drug regimens. Unfortunately, there are few treatment options after failure of first-line therapy. Ramucirumab, a human IgG1 monoclonal antibody to VEGFR-2, has been recently approved in the European Union (EU) for use as monotherapy or in combination with paclitaxel as second-line treatment in patients with advanced GC with progressed disease. We performed a cost-effectiveness analysis of the Ramucirumab plus paclitaxel doublet versus paclitaxel alone in patients with previously treated advanced GC, based on results of the RAINBOW trial (1).METHODS:A Markov model has been developed in order to estimate the Life Years Gained (LYGs) and the incremental cost-effectiveness ratio (ICER) for both treatments. The model adopted the Italian healthcare system perspective and the time horizon is that of the lifetime of a patient with an advanced GC. The model considered three distinct health states: stable, progression or death. Transition probabilities were extracted from the Kaplan-Meier curves provided in the trial and cubic/spline function was used to approximate the extrapolation of survival curves for each treatment cycle. An internal model validation was performed to validate the Overall Survival (OS) curves generated by our model simulation. We based our economic analysis on clinical data and resource consumption (drugs, drug administration, supportive care medications, disease monitoring and graded 3 or 4 adverse events) on the Italian setting (2,3). All costs were expressed in euros. Sensitivity analysis also have been performed.RESULTS:This cost-effectiveness study demonstrated that, in 2nd-line therapy, the combination of ramucirumab with paclitaxel provides an incremental benefit (+1.54) at high incremental cost (EUR41,616) per LYGs.CONCLUSIONS:At a threshold of EUR5,000 for LYGs, based on Italian perspective, ramucirumab plus paclitaxel had less probability of being cost-effective. To our knowledge, our study is the first modeling study from an Italian payer perspective and the first worldwide to examine ramucirumab as a 2nd-line treatment.

Extrapolation of Survival Curves from Cancer Trials Using External Information.

Background: Estimates of life expectancy are a key input to cost-effectiveness analysis (CEA) models for cancer treatments. Due to the limited follow-up in Randomized Controlled Trials (RCTs), parametric models are frequently used to extrapolate survival outcomes beyond the RCT period. However, different parametric models that fit the RCT data equally well may generate highly divergent predictions of treatment-related gain in life expectancy. Here, we investigate the use of information external to the RCT data to inform model choice and estimation of life expectancy. Methods: We used Bayesian multi-parameter evidence synthesis to combine the RCT data with external information on general population survival, conditional survival from cancer registry databases, and expert opinion. We illustrate with a 5-year follow-up RCT of cetuximab plus radiotherapy v. radiotherapy alone for head and neck cancer. Results: Standard survival time distributions were insufficiently flexible to simultaneously fit both the RCT data and external data on general population survival. Using spline models, we were able to estimate a model that was consistent with the trial data and all external data. A model integrating all sources achieved an adequate fit and predicted a 4.7-month (95% CrL: 0.4; 9.1) gain in life expectancy due to cetuximab. Conclusions: Long-term extrapolation using parametric models based on RCT data alone is highly unreliable and these models are unlikely to be consistent with external data. External data can be integrated with RCT data using spline models to enable long-term extrapolation. Conditional survival data could be used for many cancers and general population survival may have a role in other conditions. The use of external data should be guided by knowledge of natural history and treatment mechanisms.

Bird diversity and abundance in organic and conventional apple orchards in northern Japan.

Many studies have investigated the benefits of agri-environmental schemes, such as organic farming, on biodiversity conservation in annual systems, but their effectiveness in perennial systems is less well understood, particularly in bird communities in temperate regions of Asia. This study examined the effects of organic farming practices on species richness and abundance of breeding birds in apple orchards in northern Japan. Bird counts were conducted in six pairs of organic and conventional orchards during the breeding season in April and May 2015. The total species richness of birds, estimated by sample- and coverage-based rarefaction and extrapolation curves, was greater in organic orchards than in conventional orchards. Among the three dietary guilds (insectivore, granivore, and omnivore), only insectivorous species were more abundant in organic orchards than in conventional ones. This study offers the first quantitative evidence that organic farming can be beneficial for enhancing the diversity of birds, particularly of insectivores, in fruit orchards in Japan.

Propagation of rating curve uncertainty in design flood estimation

AbstractStatistical flood frequency analysis is commonly performed based on a set of annual maximum discharge values which are derived from stage measurements via a stage‐discharge rating curve model. Such design flood estimation techniques often ignore the uncertainty in the underlying rating curve model. Using data from eight gauging stations in Norway, we investigate the effect of curve and sample uncertainty on design flood estimation by combining results from a Bayesian multisegment rating curve model and a Bayesian flood frequency analysis. We find that sample uncertainty is the main contributor to the design flood estimation uncertainty. However, under extrapolation of the rating curve, the uncertainty bounds for both the rating curve model and the flood frequency analysis are highly skewed and ignoring these features may underestimate the potential risk of flooding. We expect this effect to be even more pronounced in arid and semiarid climates with a higher variability in floods.

Variation in White Stork (Ciconia ciconia) diet along a climatic gradient and across rural-to-urban landscapes in North Africa.

Assessing diet composition of White Storks (Ciconia ciconia) breeding under North African conditions provides key information to understanding its trophic niche for conservation purpose. Since, climate controls productivities of foraging habitats and thus food availability for predators, this study examines how Storks' diet parameters varied following a climate gradient along with rural-to-urban landscapes in north-eastern Algeria. Feeding strategies to cope with severe conditions were discussed in light of climate aridity and urbanization and how these influence reproduction, population dynamics and distribution. While invertebrate prey accounted for 94% of ingested individuals, the biomass intake was dominated by chicken remains scavenged from rubbish dumps (67%) and small mammals (14%). Generalized linear models revealed that prey numbers varied significantly between climatic regions and landscapes types, but no significant differences were observed for other dietary parameters, including prey biomass. The study showed high dietary similarity between study climates and landscapes, mainly among rural and urban colonies located in semi-arid and sub-humid areas, which differed from those in suburban and arid climate. Rarefaction and extrapolation curves indicated that prey species richness in White Stork diets was expected to be higher in urban colonies located in sub-humid climate. Despite low prey species diversity in arid regions, the White Stork demonstrates a broad trophic niche, which could be due to supplementary feeding from human refuse. This study suggests that regardless of the climate or landscape, White Storks ensure a constant food intake, despite prey biomass fluctuations, by adapting their diet. Foraging in diverse habitats, including trash dumps, ensures a sufficiently balanced diet to meet nutritional requirements.

Cost-effectiveness Analysis in R Using a Multi-state Modeling Survival Analysis Framework: A Tutorial.

This tutorial provides a step-by-step guide to performing cost-effectiveness analysis using a multi-state modeling approach. Alongside the tutorial, we provide easy-to-use functions in the statistics package R. We argue that this multi-state modeling approach using a package such as R has advantages over approaches where models are built in a spreadsheet package. In particular, using a syntax-based approach means there is a written record of what was done and the calculations are transparent. Reproducing the analysis is straightforward as the syntax just needs to be run again. The approach can be thought of as an alternative way to build a Markov decision-analytic model, which also has the option to use a state-arrival extended approach. In the state-arrival extended multi-state model, a covariate that represents patients’ history is included, allowing the Markov property to be tested. We illustrate the building of multi-state survival models, making predictions from the models and assessing fits. We then proceed to perform a cost-effectiveness analysis, including deterministic and probabilistic sensitivity analyses. Finally, we show how to create 2 common methods of visualizing the results—namely, cost-effectiveness planes and cost-effectiveness acceptability curves. The analysis is implemented entirely within R. It is based on adaptions to functions in the existing R package mstate to accommodate parametric multi-state modeling that facilitates extrapolation of survival curves.

SU‐F‐T‐64: An Alternative Approach to Determining the Reference Air‐Kerma Rate from Extrapolation Chamber Measurements

Purpose:Since 2008 the Physikalisch‐Technische Bundesanstalt (PTB) has been offering the calibration of 125I‐brachytherapy sources in terms of the reference air‐kerma rate (RAKR). The primary standard is a large air‐filled parallel‐plate extrapolation chamber. The measurement principle is based on the fact that the air‐kerma rate is proportional to the increment of ionization per increment of chamber volume at chamber depths greater than the range of secondary electrons originating from the electrode x0.Methods:Two methods for deriving the RAKR from the measured ionization charges are: (1) to determine the RAKR from the slope of the linear fit to the so‐called 'extrapolation curve’, the measured ionization charges Q vs. plate separations x or (2) to differentiate Q(x) and to derive the RAKR by a linear extrapolation towards zero plate separation. For both methods, correcting the measured data for all known influencing effects before the evaluation method is applied is a precondition. However, the discrepancy of their results is larger than the uncertainty given for the determination of the RAKR with both methods.Results:A new approach to derive the RAKR from the measurements is investigated as an alternative. The method was developed from the ground up, based on radiation transport theory. A conversion factor C(x1, x2) is applied to the difference of charges measured at the two plate separations x1 and x2. This factor is composed of quotients of three air‐kerma values calculated for different plate separations in the chamber: the air kerma Ka(0) for plate separation zero, and the mean air kermas at the plate separations x1 and x2, respectively. The RAKR determined with method (1) yields 4.877 µGy/h, and with method (2) 4.596 µGy/h. The application of the alternative approach results in 4.810 µGy/h.Conclusion:The alternative method shall be established in the future.

Artificial Neural Network Rainfall-Discharge Model Assessment Under Rating Curve Uncertainty and Monthly Discharge Volume Predictions

The accuracy of rainfall-discharge volume model predictions depends on the model design and uncertainty of the available stage-discharge measurements used to fit the rating curve, which converts a time-series of recorded stage into discharge. In general, the rating curve uncertainty is the product of several combined sources. Over Algerian rivers, the extrapolation of the rating curve beyond the gauging range is the main source of this uncertainty. This study, therefore, represents a quantitative approach to reflect rigorously the impact of the rating curve uncertainty on the improvement of monthly discharge volume prediction quality by the artificial neural network (ANN) rainfall-discharge model. The rating curve uncertainty of the Fer a cheval hydrometric station in the Mazafran watershed is performed within Bayesian analysis for stationary rating curves using the BaRatin method. This allows as to build a new time series of discharge in order to assess an ANN rainfall-discharge model. To do that, Levenberg–Marquardt back propagation neuronal network has been applied over 1972-2012 time-period, for five hydrometric stations in the Algiers Coastal Basin. The model inputs were constructed in different ways, during the algorithm development, such as precipitation, antecedent precipitation with different monthly lag times and antecedent monthly discharge volume. The results indicate that training/validation of ANN rainfall-discharge volume model is widely affected by the streamflow datasets uncertainty. A large proportion of model prediction errors are significantly improved when considering the rating curve uncertainty.

Ultrashort laser pulse ablation of copper, silicon and gelatin: effect of the pulse duration on the ablation thresholds and the incubation coefficients

In this paper, the influence of the pulse duration on the ablation threshold and the incubation coefficient was investigated for three different types of materials: metal (copper), semiconductor (silicon) and biopolymer (gelatin). Ablation threshold values and the incubation coefficients have been measured for multiple Ti:sapphire laser pulses (3 to 1000 pulses) and for four different pulse durations (10, 30, 250 and 550 fs). The ablation threshold fluence was determined by extrapolation of curves from squared crater diameter versus fluence plots. For copper and silicon, the experiments were conducted in vacuum and for gelatin in air. For all materials, the ablation threshold fluence increases with the pulse duration. For copper, the threshold increases as τ 0.05, for silicon as τ 0.12 and for gelatin as τ 0.22. By extrapolating the curves of the threshold fluence versus number of pulses, the single-shot threshold fluence was determined for each sample. For 30 fs pulses, the single-shot threshold fluences were found to be 0.79, 0.35, and 0.99 J/cm2 and the incubation coefficients were found to be 0.75, 0.83 and 0.68 for copper, silicon and gelatin, respectively.