Laser Ablation Profile Research Articles

Inferring odontocete life history traits in dentine using a multiproxy approach (δ15 N, δ44/42 Ca and trace elements).

Understanding the interactions between marine mammals and their environment is critical for ecological and conservation purposes. Odontocetes offer a continuous record of their life history from birth as recorded in annual increments of their tooth dentine. Because dentine is not remodeled and contains collagen, nitrogen stable isotope compositions (δ15 N) reflect nursing and weaning events, life history traits that would otherwise be impossible to retrieve in such elusive marine animals. Yet, capturing the magnitude and temporal changes in these events is constrained by tooth size and sampling resolution. Moreover, historical and fossil specimens undergo collagen decay, hence the need to develop the measurements of other proxies. Here, we present a multiproxy approach to investigate the use of Ca isotope compositions (δ44/42 Ca) in relation to δ15 N and laser ablation profiles for different trace metal (Ba, Mg, Sr, Zn) concentrations across the dentine of a single individual of the common bottlenose dolphin Tursiops truncatus. To help interpret the dentine data, we provide milk elemental compositions and δ44/42 Ca values for two odontocete individuals. We discuss the observed changes in δ44/42 Ca across the dentine as potential markers of birth, weaning interval, incidental ingestion of seawater, trophic level and physiology. Incidental ingestion of seawater during nursing induces a positive offset in δ44/42 Ca values recorded in the early formed dentine. Life history parameters of individual marine mammals are extremely difficult to retrieve due to limitations in observing specimens in the wild and the methodology presented here offers new ecological and paleoecological perspectives.

Customized Ablation Area PTK as a Treatment for Limewater-induced Calcium Carbonate Corneal Deposits

PURPOSE: To describe a customized ablation area photo-therapeutic keratectomy (CAA-PTK) technique to accurately match and ablate an area of calcific deposits using a laser ablation profile matching the slit-lamp findings. METHODS: A chronic non-healing epithelial defect was induced by limewater injury from a stalactite. The calcific deposits eroding the corneal anterior stromal layer were refractory to medical therapy and ulcer bed debridement. CAA-PTK tailored to exactly match the pathology dimensions was performed. RESULTS: Complete epithelial healing was observed the next day with unaltered visual acuity (corrected distance visual acuity 20/20 - ). One month postoperatively, corneal optical coherence tomography showed a healed epithelial defect with epithelial thickening over the ablated area. The patient was followed up for 2 years with no signs or symptoms of corneal erosions. CONCLUSIONS: CAA-PTK application in treating potential corneal denaturation with overlying non-healing epithelial defects refractory to stromal bed debridement is promising. Unlike conventional PTK, CAA-PTK avoids unnecessary epithelial and stromal ablation, leading to faster visual recovery. [ Journal of Refractive Surgery Case Reports. 2022;2(2):e38–e42.]

Assessing laser ablation multi-collector inductively coupled plasma mass spectrometry as a tool to study archaeological and modern human mobility through strontium isotope analyses of tooth enamel

To evaluate the possibility of obtaining detailed individual mobility data from archaeological teeth, the strontium isotope ratios on 28 human teeth from three separate Early-Mid Holocene, Swedish, foraging contexts (Norje Sunnansund, Skateholm and Västerbjers) were analysed through laser ablation. The teeth/individuals have previously been analysed using traditional bulk sampled thermal ionisation mass spectrometry. To validate the conclusions regarding the archaeological teeth, a tooth from a modern man with a known background was also analysed. The result shows that all of the teeth display less than 0.4% discrepancy between the mean values of the laser ablation profiles and the previously published bulk data and 25 (89%) of the teeth display less than a 0.2% discrepancy. By calculating linear and polynomial trendlines for each ablated tooth, it was possible to illustrate a strong correlation for the transition pattern between the measurements when following a chronological sequence from the tip to the cervix. Such correlations were not reproduced when the data sequence was randomized. The analyses show that the chronologically sequenced ablation data fit with a transition between local bioavailable strontium regions, that the measurements do not fluctuate between extremes and that their values are not caused by end-member mixing. This indicates an increasing data resolution when reducing strontium isotope ratio averaging time by minimizing the sampling area. The results suggest strontium incorporation in human teeth can be measured on an ordinal scale, with a traceable chronological order to enamel mineralization when sampled from tip to cervix at an equal distance from the surface. Micro-sampling enamel is considered a valid method to assess prehistoric, but not modern, human mobility; laser ablation technology increases the amount of information obtained from a single tooth while rendering minimal damage to the studied specimen.

FTIR and Raman as a noninvasive probe for predicting the femtosecond laser ablation profile on heterogeneous human teeth

For high precision laser surgery, noninvasive tool for prediction of laser ablation profile beforehand is imperative. The present study proposed a method to utilize nondestructive FTIR and Raman probes for predicting laser ablation profile overcoming the challenge of heterogeneity on individual target tissue. By ascribing the chemical heterogeneity of teeth drive their differential machining capability, the study establishes a correlation between the chemical composition and their ablation parameters (ω0,Deff and Fth). The chemical composition of teeth was obtained by noninvasive tools (FTIR and Raman) in terms of absorption peak intensity. To further correlate with key laser ablation parameters, the laser irradiation study was carried out using 800 nm, 100 fs, Ti:Sapphire laser. The surface morphology of irradiated sample was measured by optical profiler. A strong correlation was observed between laser ablation parameters and peak intensity of phosphate group for both FTIR and Raman spectroscopy. The concentration of phosphate group shows a positive relationship to ablation threshold fluence, while the effective Gaussian beam radius and effective energy penetration depth show negative correlation. Both nondestructive probes show good linearity which enable us to extrapolate the key laser ablation parameters for predicting laser ablation profile on random dentin and enamel samples. The ablation profiles predicted based on both FTIR and Raman are well-matched in dentin, whereas it shows a slight deviation in enamel. The predicted profiles are consistent with experimental results at lower power whereas it shows a slight deviation at higher power due to screening effect. Thus, FTIR and Raman probes can be used to predict laser ablation profile nondestructively in real-time and obviate the need for trial runs. Furthermore, the present study has predicted the laser ablation rate and ablation efficiency for performing laser surgery in optimum laser processing conditions irrespective of teeth heterogeneity.

Physiochemical characteristics: A robust tool to overcome teeth heterogeneity on predicting laser ablation profile.

To avoid excessive tissue removal and collateral damage, the high-power density laser is apt for dental surgery also need to have high precision. For high-precision dental surgery with minimal tissue damage, the present work frames a method to predict laser ablation profile based on surface morphology and chemical composition of dentin. The surface morphology and chemical composition were studied on different dentin samples using scanning electron microscope (SEM) and Energy Dispersive X-ray Analysis (EDAX), respectively. The key laser ablation parameters (ω0 , Deff , and Fth ) were determined by laser irradiation study using 800 nm, Ti:Sapphire femtosecond laser at processing condition of 100 fs, 10 kHz and 10 mm/s. The dentin samples show a strong linear correlation between physiochemical characteristics and laser ablation parameters. The surface morphology exhibits a negative linear correlation with threshold fluence, whereas the converse is true for chemical composition. The laser ablation parameters of a random dentin sample are derived from the knowledge of linearity data. From the obtained laser ablation parameters, the complete theoretical ablation profile is constructed and validated with experimental ablation profile. Even though the surface morphology of dentin shows high linearity, the concentration of Ca and P can be used as the most feasible probe in clinical settings. Furthermore, the laser ablation rate and ablation efficiency are predicted by the method to optimize the laser processing condition for any specific teeth. The versatility of the method overcomes the problem of heterogeneity on various teeth and simplifies the method of finding optimal laser processing condition for immaculate laser surgery.

Quality of life and satisfaction among physicians after wavefront-optimized vs topography-guided laser vision correction.

To assess satisfaction, quality of life, occupational impact, and clinical outcomes of physicians who have undergone laser vision correction (LVC) using either wavefront-optimized (WFO) or topography-guided (TG) excimer laser ablation profile with femtosecond laser flap creation. Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA. Retrospective survey study. A 12-question survey was sent to all physicians who underwent laser in situ keratomileusis or photorefractive keratectomy at the Cole Eye Institute between 2011 and 2018 on the WaveLight Allegretto Wave Eye-Q Laser (Alcon Laboratories, Inc.). Visual outcomes were obtained from patient charts. Two hundred thirty-five physicians (454 eyes) met the study's inclusion criteria, including 181 physicians (353 eyes) who underwent WFO LVC and 54 physicians (101 eyes) who underwent TG LVC. One hundred seventeen physicians (49.8%) responded to the survey and reported an overall satisfaction rate of 98.3% among all physicians receiving LVC with 96.6% reporting they would have the procedure again. Visual outcomes showed a high level of surgical predictability, efficacy, and safety among WFO and TG eyes, with a higher percentage of eyes that received TG ablation achieving 20/10 vision (22% vs 4%, P < .0001) and 20/15 vision (87% vs 69%, P < .01) when compared with WFO eyes. Physicians who had undergone LVC with either WFO or TG excimer laser ablation reported high satisfaction and quality-of-life improvements. Both groups achieved excellent visual outcomes, with a higher percentage of TG eyes achieving 20/10 and 20/15 vision.

Topography-Guided Refractive Astigmatism Outcomes: Predictions Comparing Three Different Programming Methods.

PurposeTo identify the laser programming strategy that will achieve optimal refractive outcomes of LASIK with a topography-guided laser for eyes with a disparity between cylinder measured by manifest refraction and cylinder measured by topography.SettingSix surgeons at 5 clinical sites in the USA.DesignRetrospective data review.MethodsPreoperative, treatment, and postoperative data on 52 eyes that underwent topography-guided LASIK with the WaveLight EX500 Contoura® Vision excimer laser ablation profile in which the vectors representing the preoperative refractive cylinder and the cylinder measured by the WaveLight® Topolyzer™ VARIO Diagnostic Device (Vario cylinder) differed by >/= 0.50D and/or >/= 10 degrees of orientation were analyzed retrospectively. Data were contributed by six surgeons using the laser at 5 different clinical sites. Vector analysis of postoperative cylindrical refractive error and the actual laser programming strategy was used to calculate the cylindrical correction that would, theoretically, have completely eliminated postoperative refractive cylinder. This was compared to expected results using the preoperative manifest cylinder, the topographic cylinder, and the Phorcides Analytic Engine (Phorcides LLC, North Oaks MN; Phorcides). For analysis, subjects were stratified on the basis of the vector difference between Manifest and Topo cylinder (High, >0.75 D; and Low, ≤0.75 D).ResultsThe poorest calculated theoretical outcomes were obtained with the manifest refraction (centroid: −0.43, 0.22; mean calculated error vector: 0.56 ± 0.42 D; p=ns). Better outcomes were obtained with the topographically measured refraction (centroid: 0.37, 0.02; mean calculated error vector: 0.47 ± 0.33 D; p=ns). The best outcomes were obtained with Phorcides (centroid: −0.15, 0.06; mean calculated error vector: 0.39 ± 0.28 D; p=ns). The mean error vector magnitude in the Phorcides Low group was significantly lower than for the Manifest and Topo Low groups (0.26 D vs 0.48 D and 0.33 D; p<0.01). The mean error magnitude in the Phorcides High group was nearly 0.25 D lower than for the Manifest High group (0.48 D vs 0.70 D; p<0.01), but was the same as for the Topo High group (0.48 D vs 0.48 D).ConclusionOur study suggests that using the topographically measured cylinder or the cylinder selected by Phorcides will produce more desirable refractive outcomes than entry of the preoperative refractive cylinder as the basis for correction of myopia and myopic astigmatism with the WaveLight Contoura Vision excimer laser.

Picosecond laser ablation and depth profile of Cu(In, Ga)Se2 thin film layer

Laser ablation based on picosecond laser was used to achieve the micro-analysis of Cu(In, Ga)Se2 (CIGS) thin film with the ablation crater diameter of 50μm and the ablation crater central depth of 93 ± 13 nm. We achieved the depth profile of CIGS thin film with different laser shot number. The evolutions of spectral lines intensities of Ca from glass substrate and Ga and In from CIGS thin film layer, and intensity ratios of Ca/Ga and Ca/In could exhibit the change of the ablation volume, which could estimate the thin film thickness of single CIGS thin film layer. The average plasma temperature was calculated to be about 5243 ± 100 K, and the average electron density was calculated to be about 4.5×1016 cm−3. It is shown that our experimental setup is suitable to achieve a precise control and monitor the element compositions in each CIGS thin film layer in the research and in the production of CIGS solar cells.

Bulk microanalysis of assemblages of small fluid inclusions by LA-ICP-MS: Methodology and application to orogenic gold systems

Microanalysis of individual fluid inclusions by laser ablation inductively coupled mass spectrometry (LA-ICP-MS) is a powerful tool for reconstructing the composition of hydrothermal fluids, but it demands a sample quality that is unattainable in many cases. In orogenic gold deposits, the need for direct fluid microanalysis has been present for several decades, but due to the high fluid flux and prolonged hydrothermal and tectonic history that typifies these systems, most samples do not meet the criteria of fluid inclusion size and distribution that allow LA-ICP-MS analysis of individual isolated fluid inclusions. To overcome this difficulty, a method has been developed and tested, whereby areas of quartz densely populated with fluid inclusions (e.g., growth zones, secondary planes) are analyzed along a single continuous laser ablation profile; the generated signals are subsequently converted to time-slice datasets and plotted as element ratios in ternary diagrams to reconstruct specific major- and trace-element ratios. The estimated fluid compositions are in good agreement with previous analytical results of the same material (microthermometry, evaporate mound and conventional LA-ICP-MS) and are shown to be geologically viable on a boarder scale when compared to literature data from similar ore environments. The method has high spatial and chemical resolution, which allows the reconstruction of micro-scale fluid chemical changes, such as significant fluctuation in the relative element concentration (e.g., K, Rb, Ba, Sr and V versus Na, Li and As) during crystal growth, as observed in one of the test samples. The significance of this bulk LA protocol is that it allows the quick, easy and cost-effective microanalysis of samples that are typically inundated with fluid inclusions, such as those in orogenic and epithermal systems, which would otherwise not be amenable for further quantitative analysis to constrain fluid chemistry.

Trace element systematics and ore-forming processes in mafic VMS deposits: Evidence from the Troodos ophiolite, Cyprus

The volcanogenic massive sulfide (VMS) deposits in the Troodos ophiolite (Cyprus) are ancient analogues for modern day seafloor massive sulfide mineralisation formed in a supra-subduction zone environment. In this study we present the first detailed in situ study of trace elements in sulfides from twenty VMS deposits hosted in the Troodos ophiolite to better understand factors that influence the distribution, enrichment and incorporation of trace elements in different sulfide minerals.On a mineral scale, trace elements exhibit systematic variations between pyrite, chalcopyrite and sphalerite. Pyrite preferentially incorporates As, Sb, Au and Te, whilst chalcopyrite is enriched in Co and Se. Sphalerite is trace element poor with the exception of Ag and Cd. Selenium averages 278 ppm (n = 150) in chalcopyrite but only 42 ppm (n = 1322) in pyrite. Bismuth and Te in pyrite show a weak positive correlation (R2 = 0.35) in some VMS deposits possibly linked with the occurrence of Bi-telluride inclusions. Trace element concentrations also vary between colloform and euhedral pyrite, with an enrichment of Au, As, Sb, Cu and Zn in colloform compared to euhedral pyrite.Time resolved laser ablation profiles reveal that the trace element distribution on a mineral scale is not uniform and varies with crystallographic effects, fluctuating physicochemical fluid conditions such as temperature, pH, fS2, fO2 and ligand availability during sulfide precipitation. Incorporation mechanisms in sulfides differ between elements in pyrite, Ag, As, Se and Pb are hosted in solid solution or as nanoscale inclusions, whilst Au, Sb and Te may form micro-scale inclusions.On a regional scale (20 km) the distribution of trace elements exhibits systematic variations between three major structural domains; namely the Solea, Mitsero and Larnaca grabens. The VMS deposits of the magmatic-tectonic Solea graben are enriched in Se, Co, Te, Au and Cu relative to Mitsero, which is a purely extensional feature. Therefore, we hypothesise that a variable magmatic volatile influx related to a) ‘magma’ volume, b) migration of the magmatic-hydrothermal crack front and associated brine liberation or c) a variation in protolith metal concentration are responsible for regional scale variations in VMS geochemistry. This is suggested to be intrinsically linked to the spreading architecture of Troodos.

Prediction of femtosecond laser ablation profile on human teeth.

To predict the laser ablation profile on dental hard tissue which will enable the user to optimize laser parameters so as to carry out the laser treatment with minimal tissue damage. The present study constructs a mathematical model to predict the ablation profile based on Gaussian beam distribution of laser intensity and correlates the model with experimentally obtained ablation parameters (effective Gaussian beam radius, ablation threshold fluence, and effective energy penetration depth). To obtain the ablation parameters, laser ablation experiments were carried out on dental hard tissues using Ti:Sapphire femtosecond laser (800nm, 100fs, 10kHz). The method is further extended to predict the ablation rate and efficiency as well. The profile predicted from the mathematical model is compared with that of experimental results. It is found that the predicted ablation profile agrees well with the experimental profile for both enamel and dentin except a slight deviation at higher fluence for dentin. The calculated ablation rate is comparable to that of experimental results whereas for ablation efficiency appreciable deviation is observed in the case of dentin. The model succinctly predicts the ablation profile, ablation rate, and ablation efficiency which will enable to perform dental surgery at optimized laser processing conditions with high precision thus reducing the tissue damage appreciably. Once the details of lesion are known through proper diagnostic tools, the method enables the user to readily obtain optimum laser parameters. It can be used as a handy reference for dentists to perform damage-free surgery, ensuring quicker healing.

Presbyopic Excimer Laser Ablation: A Review.

To provide an overview of the efficacy and safety of available presbyopic excimer laser ablation profiles. Literature review. Monovision with excimer laser traditionally applies near correction to the non-dominant eye. Different excimer laser presbyopic approaches include the increase in depth of focus, through the controlled change of spherical aberration or asphericity, or multifocal ablation patterns with central or peripheral near vision zones. The studies investigating different excimer laser ablation patterns applied in previously myopic eyes revealed high levels of efficacy with all ablation profiles (between 68% and 99% achieving binocular uncorrected distance visual acuity [UDVA] of 20/25 or better, and between 70% and 100% achieving uncorrected near visual acuity [UNVA] presenting J3 or better). In hypermetropic eyes, most of the studies revealed high levels of efficacy with different platforms (between 78% and 100% achieving binocular UDVA of 20/25 or better and between 70% and 100% achieving UNVA presenting J3 or better). Loss of two or more lines of corrected distance visual acuity varied between 0% and 10% in the myopic eyes and between 0% and 14% in the hyperopic eyes. There is evidence that excimer laser presbyopic strategies accomplish spectacle independence at reasonable levels. There are reliable and safe options for both myopic and hyperopic eyes with satisfactory outcomes regarding near and distance vision. [J Refract Surg. 2018;34(10):698-710.].

Corneal Stability following Hyperopic LASIK with Advanced Laser Ablation Profiles Analyzed by a Light Propagation Study.

Purpose To assess anterior corneal surface stability 12 months following hyperopic LASIK correction with a light propagation algorithm. Setting Vissum Instituto Oftalmológico de Alicante, Universidad Miguel Hernández, Alicante, Spain. Methods This retrospective consecutive observational study includes 37 eyes of 37 patients treated with 6th-generation excimer laser platform (Schwind Amaris). Hyperopic LASIK was performed in all of them by the same surgeon (JLA) and completed 12-month follow-up. Corneal topography was analyzed with a light propagation algorithm, to assess the stability of the corneal outcomes along one year of follow-up. Results Between three and twelve months postoperatively, an objective corneal power (OCP) regression of 0.39 D and 0.41 D was found for 6 mm and 9 mm central corneal zone, respectively. Subjective outcomes at the end of the follow-up period were as follows: 65% of eyes had spherical equivalent within ±0.50 D. 70% of eyes had an uncorrected distance visual acuity 20/20 or better. 86% of eyes had the same or better corrected distance visual acuity. In terms of stability, 0.14 D of regression was found. No statistically significant differences were found for all the study parameters evaluated at different postoperative moments over the 12-month period. Conclusions Light propagation analysis confirms corneal surface stability following modern hyperopic LASIK with a 6th-generation excimer laser technology over a 12-month period.

Design of LTCC Based 3-D Antenna for Sub-THz Application

In the paper, selected aspects of LTCC technology for fabrication of passive elements for microwave application are presented. The research effect is based on the example of experimental 3-D antenna performed for a sub-THz scanner. For the described methods of antennas performance the achieved printing quality have been determined basing on observations using a digital microscope Hirox KH7700 and measurements of geometrical dimensions. The impact of geometrical structure dimensions and printed pattern resolution on its working abilities is also discussed. The main emphasis of the research work is on high resolution metallization obtainment by modification of screen printing parameters and conditions (the angle and pressure of squeegee, the mesh size), laser ablation and co-firing profile.

Optimizing LA-ICP-MS analytical procedures for elemental depth profiling of foraminifera shells

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is becoming a widespread technique for analyzing elemental ratios in foraminiferal calcite. Here we focus on optimizing LA-ICP-MS for high-resolution depth profiling of elemental ratios through shell walls. This application reveals intrashell variability and provides a unique opportunity to quantify trace element incorporation over short time scales of calcification by an individual foraminifer. High-resolution depth profiling requires careful consideration of both ablation and analytical conditions required to resolve differences in shell chemistry across sub-micron shell thickness. We present laser ablation profiles of NIST SRM 610 standard glass data (in cps) and elemental/Ca ratios (in mmol/mol) from foraminiferal calcite obtained over a range of operating conditions using a Photon Machines 193nm UV excimer laser-ablation system, equipped with a dual-volume ANU HelEx chamber, coupled to an Agilent 7700x quadrupole ICP-MS. Different combinations of energy density, repetition rate, and mass spectrometer cycle time can yield varying elemental profiles. This variability can mimic and/or mask real intrashell trace element heterogeneity in foraminifer shells. At low (<3Hz) laser repetition rates, real intrashell element variation can be obscured depending on the laser energy, whereas using moderate (≥3Hz) laser repetition rates and/or a signal-smoothing device improves the accuracy and precision of intrashell trace element profiles. Shell material is ablated rapidly when using a 5Hz or greater repetition rate and an energy density of 3J/cm2 or greater, resulting in reduced spatial resolution.

Femtosecond laser–assisted hyperopic laser in situ keratomileusis with tissue-saving ablation: Analysis of 800 eyes

To evaluate the results and complications of hyperopic laser in situ keratomileusis (LASIK) with a low-energy femtosecond laser and non-custom tissue-saving ablation profile. Private practice, Siena, Italy. Case series. Hyperopic eyes with a spherical equivalent (SE) between +1.0 and +6.5 diopters (D) had LASIK. The flap (nominal thickness 110 μm) was created with a Ziemer LDV Z2 femtosecond laser and the refractive ablation performed with a Technolas 217P excimer laser in tissue-saving mode. Eight hundred eyes of 413 patients were treated. The mean preoperative values were SE, +3.41 D ± 1.16 (SD); defocus equivalent, 4.20 ± 1.33; corrected distance visual acuity (CDVA), 0.07 ± 0.08 logMAR. At 9 months, the mean SE was -0.06 ± 0.26 D and the mean defocus equivalent 0.68 ± 0.62 (both P<.05). The defocus equivalent was 0.50 D or less in 594 eyes (74.3%) and 1.00 D or less in 707 eyes (88.4%). The mean CDVA was 0.07 ± 0.06 logMAR; 3 eyes (0.4%) lost 2 lines of CDVA and 58 eyes (7.3%) lost 1 line. The mean uncorrected distance visual acuity was 0.16 ± 0.13 logMAR. The safety index was 1.0 and the efficacy index, 0.8. The mean root-mean-square induced primary spherical aberration was 0.65 μm and the mean induced primary coma, 0.24 μm (both P<.05). The low incidence of femtosecond-related complications was associated with good predictability, safety, and a low retreatment rate. The mean flap was 7 μm thicker than expected. The author has no financial or proprietary interest in any material or method mentioned.

Multiple zone multifocal phase designs

New multifocal phase designs aiming at expanding depth of focus in the presbyopic eye are presented. The designs consist of multiple radial or angular zones of different powers or of combined low- and high-order aberrations. Multifocal performance was evaluated in terms of the dioptric range for which the optical quality is above an appropriate threshold, as well as in terms of the area under the through-focus optical quality curves. For varying optical power designs optimal through-focus performance was found for a maximum of three to four zones. Furthermore adding more zones decreased the optical performance of the solution. Angular zone designs provided better multifocal performance (1.95 times on average) than radial zone designs with identical number of zones and the same power range. The optimal design (angular design with three zones) surpassed by 33% the multifocal performance of a bifocal angular zone design and by 32% a standard multifocal phase plate with induced spherical aberration only. By using combinations of low- and high-order aberrations the through-focus range can be extended further by another 0.5D beyond that of the best design of varying optical power. These designs can be implemented in adaptive optics systems for testing their visual performance in subjects and converted into multifocal contact lenses, intraocular lenses, or presbyopic corneal laser ablation profiles.

Theoretical analysis of wavefront aberration caused by treatment decentration and transition zone after custom myopic laser refractive surgery

To analyze the induced wavefront aberrations caused by treatment decentration and transition zone after custom myopic laser refractive surgery. Refractive Surgery Center, Tianjin Eye Hospital & Eye Institute, Tianjin Medical University, Tianjin, China. Cohort study. Wavefront aberration data from potential refractive surgery candidates were used. Based on the preoperative wavefront aberrations, the custom ablation profile was computed. Then, the influence of treatment decentration and especially that of the transition zone on induced wavefront aberrations was studied. The impact of angle mismatch on induced aberrations was analyzed. Data from 117 eyes (77 patients) were analyzed. The transition zone played a significant role in the influence of decentration on the induced aberrations in refractive surgery. Induced coma and spherical aberration increased rapidly as the lateral translation increased, and coma was significantly larger than other Zernike aberration terms. The induced aberrations from decentration with oblique incidence in the laser ablation profile were less than in the actual laser ablation process for slight subclinical decentration. The induced aberrations were not closely related to the subclinical unmatched angle from eye cyclotorsion. The induced aberrations from lateral translation were correlated with the position vector. The transition zone was designed to smooth the transition from the optical zone to the untreated cornea, and it mainly dominated induced coma and spherical aberration. To achieve the best postoperative visual performance, the effect of the transition zone in refractive surgery should be taken into account, especially for scotopic pupils.

Trace element variability in crust-bearing and non crust-bearing Neogloboquadrina incompta, P–D intergrade and Globoconella inflata from the Southwest Pacific Ocean: Potential paleoceanographic implications

Mg/Ca and Sr/Ca ratios were measured in the sub-surface dwelling planktonic foraminifera Neogloboquadrina incompta, Neogloboquadrina pachyderma–Neogloboquadrina dutertrei (P–D) intergrades and Globoconella inflata from core–top, dredge and plankton tow material from the Southwest Pacific Ocean. The presence of outer crusts on each foraminifera test was determined using a scanning electron microscope, after trace element analysis using laser ablation inductively coupled plasma mass spectrometry (LA–ICPMS). Our laser ablation profiles allow an arbitrary distinction between crust and inner calcite Mg/Ca values, with the former exhibiting consistently lower Mg/Ca by up to 56% depending on both the species and core–top location analyzed. The lower crust Mg/Ca values suggest that 1) crust formation may be initiated at a specific (low) temperature or, 2) crust-calcite no longer follows the Mg to Ca thermodynamic relationship typically associated with foraminiferal primary calcite. For Sr/Ca ratios, we did not observe any difference between crust in and inner calcite. The thickness of the crust between measured individual chambers varied, such that whole test Mg/Ca were affected by variable crustal thickness across all chambers. This study shows that increasing ratios of crust to non crust-bearing tests in N. incompta, P–D intergrades and G. inflata have the potential to lower the bulk composition of Mg/Ca, thus resulting in biased cooler temperature reconstructions.

Evidence for dietary change but not landscape use in South African early hominins

The dichotomy between early Homo and Paranthropus is justified partly on morphology. In terms of diet, it has been suggested that early Homo was a generalist but that Paranthropus was a specialist. However, this model is challenged and the issue of the resources used by Australopithecus, the presumed common ancestor, is still unclear. Laser ablation profiles of strontium/calcium, barium/calcium and strontium isotope ratios in tooth enamel are a means to decipher intra-individual diet and habitat changes. Here we show that the home range area was of similar size for species of the three hominin genera but that the dietary breadth was much higher in Australopithecus africanus than in Paranthropus robustus and early Homo. We also confirm that P. robustus relied more on plant-based foodstuffs than early Homo. A South African scenario is emerging in which the broad ecological niche of Australopithecus became split, and was then occupied by Paranthropus and early Homo, both consuming a lower diversity of foods than Australopithecus.