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MeV ion exposure behavior of PMMA resist polymer studied by synchrotron light spectroscopies
No full textThe behaviour of poly-(methyl methacrylate) (PMMA) resist exposed with 2 MeV¹ H⁺ and 6 MeV¹² C³⁺ ions has been investigated by using the photo-electron spectroscopy (PES) and X-ray absorption spectroscopy (XAS) techniques. Preliminary PES results were difficult to analyse without special precautions to counteract surface charging. XAS was on the other hand almost insensitive to the effects of surface charging. XAS investigations of the bonding in the near surface and deeper in PMMA revealed significant changes of the bonding of carbon atoms at fluences correspond to clearing (positive resist mode) and cross-linking (negative resist mode). In the clearing fluence regime the C=C bonds increase in the surface and at greater depths which is consistent with our earlier work with Raman spectroscopy. In the high fluence regime where cross-linking takes place, a reduction of C-O and C=O bonding is seen which might be indicative that the cross linking is associated with side-chain scission
Proceedings of the 2018 Undergraduate Research Conference
No full textProceedings of the 2018 Undergraduate Research Conference, University of Louisiana at Lafayette, November 16-17, 2018. Supported by the University Honors Program, Office of the Vice-President for Research, LaCOEUR, College of Liberal Arts, College of Sciences, and College of Engineering
Explaining Civilian Attacks: Terrorist Networks, Principal-Agent Problems and Target Selection
No full textTerrorist groups exhibit variation in their targeting choices. Why do some groups direct their violence against civilians while others limit this occurrence? This study analyzes the network relationships between terrorist groups to elucidate their targeting behavior. Drawing upon insights from the organizational ecology and conflict literatures, we predict that terrorist group affiliates will be significantly more likely than their parent group to attack civilian targets. Our original principal-agent theory consistently outperforms extant explanations in a multi-method analysis of 238 terrorist groups from 1998 to 2005. These results shed new light on why certain terrorist groups are more likely than others to target civilians
Investigation of mercury pathways from dental amalgam by micro-PIXE
Get PDFMercury amalgams are still widely used in dentistry in many countries. There is considerable concern about uptake of Hg in both the patient and environment. It is an interesting question if the pathway is by Hg diffusion through the tissue of the tooth or dissolution in saliva or direct evaporation through inhaled air into the lung. Our previous study [1] of a high-Cu amalgam showed no evidence of diffusion through the enamel. However, a compositional change was observed on the biting surface of the amalgam which is indicative of tribochemical changes. To investigate if the above observation was true for other types of amalgam, 17 adult teeth with amalgam obtained as operation-waste from dental clinics. The samples were embedded and sliced into 1mm sections in the coronal plane of the tooth using a low/speed diamond saw with water-based cooling. Subsequently, the slices were mechanically polished in such way that polishing debris was swept away from the sample. Micro-PIXE with 2 MeV protons was carried out in vacuum using a standard Oxford –triplet configuration. In common with our previous study [1], sharp interfaces between the enamel and amalgam were observed with no strong evidence for Hg diffusion in the enamel. Little evidence exists consistent with the presence of tribochemical alteration by mastication. However, Zn was observed to be localized at different sites in the amalgam/enamel interface
Time detector design for Time-of-Flight Elastic Recoil Detection Analysis (ToF-E ERDA) revisited
No full textTime-of-flight-energy elastic recoil detection analysis (ToF-E ERDA) is a uniquely powerful thin-film analytical technique because it can be used to measure simultaneously the depth distributions of all elements in a thin-film sample. The basic design of the time detectors which are generally based on the electron mirror has not changed significantly over 25 years or so. A classic electron optical study has been made to elucidate the factors that limit the time resolution of electron mirror time pick off detectors and how they are interrelated. Degradation of the time resolution is mainly associated with the electron divergence from an ideal straight trajectory and variations in the propagation of electromagnetic pulses over the anode surface. A set of equations that can be used to optimise time detector design are presented along with a new configuration that has an expected time resolution of 40 ps fwhm and overcomes most of the drawbacks of the conventional configuration
Irradiation effects of MeV protons on dry and hydrated Brassica rapa seeds
No full textAlthough space radiation is a known risk for space travel and eventual colonization of Moon or Mars, relatively few data exist on radiation effects on potential crop plants. We studied ���������������� �������� to assess the tolerance of seeds and seedlings to radiation by exposing dry and hydrated ��. �������� seeds to 1, 2 and 3 MeV proton ions of various fluences and examined the effect on germination and root growth. Modeling penetration depth with SRIM code indicated that the applied energy was insufficient to penetrate the seeds; therefore, all energy was deposited into the tissue. Subsequent germination varied based on the incident ion energy and fluence (dose). Dry and hydrated seeds germinate after ion fluence (10¹³ ions cm⁻²) irradiation, but the germination percentage decreased with increasing fluence for ions that could penetrate the seed coat (\u3e 1 MeV). Despite their greater volume and mass, hydrated seeds were more sensitive to irradiation than dry seeds. Damage of the seed coat after irradiation led to faster germination and initial seedling growth. Our results suggest that the seed coat represents a valuable natural radiation protection and that low energy protons, the prevailing solar radiation, are suitable for studying radiation effects in seeds and plants
Inexpensive Simple Extraction of Trace PAHs from Water using PS- DVB Monolithic Beads
Get PDFA new simple and sensitive analytical technique based on polystyrene-divinyl benzene (PS-DVB) monolithic bead extraction followed by gas chromatography–mass spectroscopic detection (GC-MS) was developed for the determination of polycyclic aromatic hydrocarbons (PAHs) in water. The PS-DVB monolithic bead was fabricated and used as the adsorbent. The experimental parameters controlling the performance of the bead extraction were optimized. Calibration curves showed excellent linear fits, with r2 \u3e0.995 for all PAHs in the 2–30,000 ng mL-1 range. The limits of detection (LODs) ranged from 0.01 to 0.47 ng mL-1. Recoveries of the PAHs in environmental water samples spiked at a concentration of 500 ng mL-1 were 72-109%, while they were 69-114% for water spiked at 20 ng mL-1. Both intraday and interday repeatabilities were high, with RSDs for 16 PAHs spiked standard solutions being less than 10%. The present study indicated that the proposed method is well suited for the quantification of PAHs in environmental and drinking water samples
Fabrication of high-transmission microporous membranes by proton beam writing-based molding technique
Get PDFPorous membranes are widely used as filters in a broad range of micro and nanofluidic applications, e.g. organelle sorters, permeable cell growth substrates, and plasma filtration. Conventional silicon fabrication approaches are not suitable for microporous membranes due to the low mechanical stability of thin film substrates. Other techniques like ion track etching are limited to the production of randomly distributed and randomly orientated pores with non-uniform pore sizes. In this project, we developed a procedure for fabricating high-transmission microporous membranes by proton beam writing (PBW) with a combination of spin-casting and soft lithography. In this approach, focused 2 MeV protons were used to lithographically write patterns consisting of hexagonal arrays of high-density pillarsof few μm size in a SU-8 layer coated on a silicon wafer. After development, the pillars were conformably coated with a thin film of poly-para-xylylene (Parylene)-C release agent and spin-coated with polydimethylsiloxane (PDMS). To facilitate demolding, a special technique based on the use of a laser-cut sealing tape ring was developed. This method facilitated the successful delamination of 20-μm thick PDMS membrane with high-density micropores from the mold without rupture or damage
Different Departments, Same Goals: Improving User Experience through Collaboration
Get PDFThe staff of Reference and Research Services at Edith Garland Dupré Library, University of Louisiana at Lafayette, determined that instructors and students of the School of Music & Performing Arts had difficulty locating scores for particular pieces of music due to no contents note in the catalog records. Reference brought this to Cataloging’s attention and suggested editing the MARC record contents note in SirsiDynix Workflows themselves.   Cataloging considered the feasibility of this course of action as well as other alternatives, such as purchasing enhanced records from a vendor. Ultimately, Cataloging discovered a workflow using MarcEdit and OCLC Connexion batch processing that automated the editing for some of the records. This method had a fast turnaround time at no cost. After this was done, Reference and Cataloging staff worked together to determine a workflow for manually enhancing the remaining records.  Partnerships between public services and technical services improve user experience and fulfill the mission of the library