Is UV laser ablation a suitable tool for geochemical analysis of organic rich source materials?

Abstract not available

Potential of short wavelength laser ablation of organic materials

Although the literature contains several articles on UV laser ablation of synthetic polymers [1] and human tissue for surgical applications, to our knowledge there is no published record on organic geochemical applications for UV laser pyrolysis–gas chromatography–mass spectrometry (LA-GC-MS). In this study we have demonstrated the use of a 213 nm UV laser beam for ablating kerogens and organic rich rocks to liberate and analyse hydrocarbon signatures and compared the results against IR laser pyrolysis and traditional Py-GC-MS. It is possible to equate laser wavelength to electron volts where 1064 nm (IR) = 1.2 eV and 213 nm (UV) = 5.8 eV. Most chemical bonds have an energy between 2-4 eV and C-C bonds are ~3.6 eV. Organic materials can absorb radiation from a UV laser and chemical bonds can be cleaved cleanly by complex photochemical pathways by a single photon [2]. Ablation occurs with almost no heating of the sample and hence the term laser ablation instead of pyrolysis. Visible or IR lasers have insufficient energy to break bonds with a single photon this results in the heating of sample by the absobtion of energy into the vibrational modes of the molecule which can then result in pyrolysis. A solvent-extracted kerogen consisting mainly of higher plant material (Brownie Butte, Montanna, ~ 70 Ma) was used for initial experiments. A number of other samples have also been analysed. Laser ablation work was performed off-line in a static helium cell followed by solvent extraction of the laser cell. Separate analysis of the same samples using a more traditional flash pyrolysis approach was performed with a CDS pyroprobe and IR laser pyrolysis [3] for comparative purposes. As can be seen in Fig 1 UV laser ablation is able to liberate relatively high molecular weight fragments with no alkenes or other pyrolysis artefacts detected. SEM images of ablation pits indicate there is no obvious thermal alteration of the sample. The results of the pyrolysis techniques (on-line and IR laser pyrolysis) are similar and display a number of artefacts related to the pyrolysis process. Laser ablation of a number of samples has also shown that the distributions of biomarkers are comparable with the solvent extracts. Product yields although not quantified appear to be much higher than traditional pyrolysis technique

Improving Outcomes with Surgical Resection and Other Ablative Therapies in HCC

With rising incidence and emergence of effective treatment options, the management of hepatocellular carcinoma (HCC) is a complex multidisciplinary process. There is still little consensus and uniformity about clinicopathological staging systems. Resection and liver transplantation have been the cornerstone of curative surgical treatments with recent emergence of ablative techniques. Improvements in diagnostics, surgical techniques, and postoperative care have lead to dramatically improved results over the years. The most appropriate treatment plan has to be individualised and depends on a variety of patient and tumour-related factors. Very small HCCs discovered on surveillance have the best outcomes. Patients with advanced cirrhosis and tumours within Milan criteria should be offered transplantation. Resection is best for small solitary tumours with preserved liver function. Ablative techniques are suitable for low volume tumours in patients unfit for either resection or transplantation. The role of downstaging and bridging therapy is not clearly established

Advancing Arts Education through an Expanded School Day: Lessons from Five Schools

In schools across the country, educators recognize the power of the arts to change young lives. They know that students' sustained engagement with enriching, high-quality experiences in the arts promotes essential skills and perspectives -- like the capacity to solve problems, express ideas, harness and hone creativity, and persevere toward a job well done. And yet today, educators at many schools that operate with conventional schedules are forced to choose between offering their students valuable opportunities to pursue the arts and focusing on other rigorous core classes that also are necessary for success in the 21st century. This study, which highlights an exciting new approach, is produced by the National Center on Time & Learning (NCTL), an organization dedicated to expanding learning time to improve student achievement and enable a well-rounded education, with support from The Wallace Foundation, a national philanthropy seeking to improve education and enrichment for disadvantaged children. In these pages, we present portraits of five schools that are advancing arts education through an expanded school day as they create vibrant and inclusive models of truly enriching education for all students

Simulated Effect of Carbon Black on High Speed Laser Transmission Welding of Polypropylene With Low Line Energy

Laser welding is an important manufacturing tool for a wide variety of polymer products including consumer goods, automotive components and medical devices. The laser process parameters and polymer properties have a significant impact on weld quality. Due to higher heat density generated by the laser transmission welding (LTW) technique, defining a set of suitable parameters for LTW of thermoplastics and composites can be challenging. In this work the effect of carbon black along other control parameters has been investigated for high speed welding using a laser source of 980 nm wavelength with low line energy. In this work, the finite element method (FEM)-based software COMSOL Multiphysics is used to create a 3D transient thermal model for LTW of isotactic polypropylene (iPP) and its composites with carbon black (CB) of concentrations ranging from 0.5 wt% to 1.5 wt%. The design of experiments based on Box-Behnken design (BBD) is used to organize the simulation experiments and mathematical models are developed based on multiple curvilinear regression analysis on the simulation findings. Independent control variables include the laser power, welding speed, beam diameter, and carbon black content in the absorbent polymer. The maximum weld temperature, weld width, and weld depth within the transmissive and absorptive layers are considered as dependent response variables. Furthermore, sensitivity analysis is carried out to investigate the impact of carbon black along with other independent variables on the responses. The welding feasibility check was performed on the basis of melt and degradation temperature of the materials, and weld depths of transmissive and absorptive layers. It has been observed that the composites containing 0.5 wt% and 1 wt% of CB can be welded successfully with neat iPP. However, due to a degradation temperature problem, composites having a larger proportion of CB (>1 wt%) appear to be more difficult to weld

GeneXplorer: an interactive web application for microarray data visualization and analysis

BACKGROUND: When publishing large-scale microarray datasets, it is of great value to create supplemental websites where either the full data, or selected subsets corresponding to figures within the paper, can be browsed. We set out to create a CGI application containing many of the features of some of the existing standalone software for the visualization of clustered microarray data. RESULTS: We present GeneXplorer, a web application for interactive microarray data visualization and analysis in a web environment. GeneXplorer allows users to browse a microarray dataset in an intuitive fashion. It provides simple access to microarray data over the Internet and uses only HTML and JavaScript to display graphic and annotation information. It provides radar and zoom views of the data, allows display of the nearest neighbors to a gene expression vector based on their Pearson correlations and provides the ability to search gene annotation fields. CONCLUSIONS: The software is released under the permissive MIT Open Source license, and the complete documentation and the entire source code are freely available for download from CPAN

Expanding the toolbox for dating basaltic lava sequences: ⁴⁰Ar–³⁹Ar dating of silicic volcanic glass from interbeds

40Ar–39Ar dating of glass shards from silicic tuffs of the Ellensburg Formation (NW, USA) interbedding basaltic lavas yielded accurate, precise, reproducible plateau and isochron ages that are within error at the 2σ level. The age-spectra have flat plateaus and the inverse isochrons have atmospheric 40Ar–36Ar at the 2σ level. Ages of 12.00 ± 0.24 Ma, 11.37 ± 0.15 Ma, 10.67 ± 0.21 Ma, 10.70 ± 0.18 Ma are consistent with the stratigraphy of four of the dated layers, the age of 10.77 ± 0.18 Ma for a fifth layer is at odds with the stratigraphy. This discrepancy arises due to the effect of glass alteration that induced K- and Ar-loss. There is no evidence of excess 40Ar–39Ar recoil. The new ages indirectly constrain the timing of eruption of the lavas above and below the ash beds. This demonstrates that volcanic glass from interbeds can be used as an additional tool for indirectly dating basaltic lava sequences, that is independent of the lavas, and complementary to other materials. Considering the numerous studies in which volcanic glass failed to provide reliable 40Ar–39Ar ages, additional and supportive constraints are still needed to assess the validity of the ages from glass shards

On the Application of Vickers Micro Hardness Testing to Isotactic Polypropylene

Hardness is a useful measure of a material’s resistance to permanent indentation; but for viscoelastic polymers, hardness data are highly dependent on the test type and the parameter set chosen. Vickers microhardness testing is used to leave small indents (<150 µm) and is shown to be applicable to polymers. A detailed investigation of the required steps for microhardness testing in isotactic polypropylene (iPP) is provided. Samples should be mounted in epoxy resin in order to maintain curing temperatures at room temperature. Mounted samples can be ground and polished in a semi-automatic polisher using graduated SiC paper (wet grinding) but progressing onto alumina suspension for polishing. Final polishing should be performed with 0.05-µm alumina suspension. The hardness measured was shown to be dependent on load and dwell time with a much greater dependency on dwell time. Strain recovery was shown to be completed after a time period equal to the dwell time. This study shows that indents can be measured thereafter, and it is recommended that they be measured within a 24 h period after the indent was created. After data fitting, the equation for hardness was shown to follow a power law with load and dwell time as the main variables. Fitting parameters were compared to those found in the literature, and it was found that parameters were significantly different to those reported elsewhere. Therefore, this study highlights the importance of calibrating on a case-by-case basis. Finally, to show the usefulness of the Vickers micro-hardness testing method, the calibrated test method was applied on iPP with additions of carbon black up to 3 wt.%. Comparisons were made with data from the literature, but the hardness data generated in our work were found to be at least twice that reported in the literature. The testing parameters were not cited in the literature: specifically, the dwell time was not provided, and this generated doubt on the usefulness of the cited data. Hence, this work is intended to serve as an exemplar of how to prepare and proceed with hardness testing of polymers