Embedded Ribbons of Graphene Allotropes: An Extended Defect Perspective

Four fundamental dimer manipulations can be used to produce a variety of localized and extended defect structures in graphene. Two-dimensional templates result in graphene allotropes, here viewed as extended defects, which can exhibit either metallic or semiconducting electrical character. \emph{Embedded allotropic ribbons}--i.e. thin swaths of the new allotropes--can also be created within graphene. We examine these ribbons and find that they maintain the electrical character of their parent allotrope even when only a few atoms in width. Such extended defects may facilitate the construction of monolithic electronic circuitry.Comment: 24 pages, 21 figure

Seven Channel Multi-collector Isotope Ratio Mass Spectrometer

A new magnetic sector mass spectrometer that utilizes seven full-sized discrete dynode electron multipliers operating simultaneously has been designed, constructed and is in preliminary testing. The instrument utilizes a newly developed ion dispersion lens that enables the mass dispersed individual isotope beams to be separated sufficiently (35 mm) to allow a full-sized discrete dynode pulse counting multiplier to be used for each beam. The ion dispersion lens is a two element electrostatic 90 degree sector device that causes the beam-to-beam dispersion to increase faster than the intra-beam dispersion. Each multiplier is contained in an isolated case with a deflector/condenser lens at the entrance. A 9-sample filament cartridge is mounted on a micro-manipulator two-axis stage that enables adjustment of the filament position with 10 micron resolution within the ion lens. Results of initial testing with actinides will be presented

Anti-Prion Drug mPPIg5 Inhibits PrPC Conversion to PrPSc

Prion diseases, also known as transmissible spongiform encephalopathies, are a group of fatal neurodegenerative diseases that include scrapie in sheep, bovine spongiform encephalopathy (BSE) in cattle and Creutzfeldt-Jakob disease (CJD) in humans. The 'protein only hypothesis' advocates that PrPSc, an abnormal isoform of the cellular protein PrPC, is the main and possibly sole component of prion infectious agents. Currently, no effective therapy exists for these diseases at the symptomatic phase for either humans or animals, though a number of compounds have demonstrated the ability to eliminate PrPSc in cell culture models. Of particular interest are synthetic polymers known as dendrimers which possess the unique ability to eliminate PrPSc in both an intracellular and in vitro setting. The efficacy and mode of action of the novel anti-prion dendrimer mPPIg5 was investigated through the creation of a number of innovative bio-assays based upon the scrapie cell assay. These assays were used to demonstrate that mPPIg5 is a highly effective anti-prion drug which acts, at least in part, through the inhibition of PrPC to PrPSc conversion. Understanding how a drug works is a vital component in maximising its performance. By establishing the efficacy and method of action of mPPIg5, this study will help determine which drugs are most likely to enhance this effect and also aid the design of dendrimers with anti-prion capabilities for the future

Induction of apoptosis in human cancer cells by targeting mitochondria with gold nanoparticles

A major challenge in designing cancer therapies is the induction of cancer cell apoptosis, although activation of intrinsic apoptotic pathways by targeting gold nanoparticles to mitochondria is promising. We report an in vitro procedure targeting mitochondria with conjugated gold nanoparticles and investigating effects on apoptosis induction in the human breast cancer cell line Jimt-1. Gold nanoparticles were conjugated to a variant of turbo green fluorescent protein (mitoTGFP) harbouring an amino-terminal mitochondrial localization signal. Au nanoparticle conjugates were further complexed with cationic maltotriose-modified poly(propylene imine) third generation dendrimers. Fluorescence and transmission electron microscopy revealed that Au nanoparticle conjugates were directed to mitochondria upon transfection, causing partial rupture of the outer mitochondrial membrane, triggering cell death. The ability to target Au nanoparticles into mitochondria of breast cancer cells and induce apoptosis reveals an alternative application of Au nanoparticles in photothermal therapy of cancer

Molecular beam surface analysis. 1993 Summary report

The Molecular Beam Surface Analysis (MBSA) program is developing both laboratory-based and potentially field-portable chemical analyses systems taking advantage of new surface analysis technology developed at the Idaho National Engineering Laboratory (INEL). The objective is to develop the means to rapidly detect and identify, with high specificity and high sensitivity, nonvolatile and low volatile organics found in Chemical Weapons (CW) and High Explosives (HE) feedstocks, agents, and decomposition products on surfaces of plants, rocks, paint chips, filters, smears of buildings, vehicles, equipment, etc.. Ideally, the method would involve no sample preparation and no waste generation, and would have the potential for being implemented as a field-portable instrument. In contrast to existing analytical methods that rely on sample volatility, MBSA is optimized for nonvolatile and low volatile compounds. This makes it amenable for rapidly screening field samples for CW agent decomposition products and feedstock chemicals and perhaps actual agents. In its final configuration (benchtop size) it could be operated in a non-laboratory environment (such as an office building) requiring no sample preparation chemistry or chemical supplies. It could also be included in a mobile laboratory used in on-site, ore remote site cooperative surveys, or in a standard laboratory, where it would provide fast screening of samples at minimal cost

Multi-collector Isotope Ratio Mass Spectrometer -- Operational Performance Report

This report describes the operational testing of a new magnetic sector mass spectrometer that utilizes seven full-sized discrete dynode electron multipliers operating simultaneously. The instrument includes a newly developed ion dispersion lens that enables the mass dispersed individual isotope beams to be separated sufficiently to allow a full-sized discrete dynode pulse counting multiplier to be used to measure each isotope beam. The performance of the instrument was measured using SRM 996 (244Pu spike) at loadings of 2.4 and 12 fg on resin beads and with SRM 4350B Columbia River Sediment samples. The measured limit of detection (3s) for 240Pu was 3.4 attograms for SRM 996. The limit of quantitation (LOQ), defined as 10 s, was 11.2 attograms. The measured concentration of 239Pu in the CRS standard was 152 ± 6 fg/g

Reactivity Initiated Accident Test Series RIA Scoping Test Quick Look Report

The Reactivity Initiated Accident Scoping Test (RIA-ST) was successfully completed August 30, 1978. The test was introductory to the RIA Series 1 tests and was designed to investigate and resolve several anticipated problem areas prior to performance of the first test of the series, Test RIA 1-1. The RIA Scoping Test, as performed, consisted of four separate single-rod experiment phases. The first three phases were performed with shrouded fuel rods of 5.8 wt.% enrichment. They were subjected to power bursts resulting in total fuel surface energies ranging from 205 to 261 cal/q at the axial peak elevation. The fourth phase consisted of a 20 wt.% enriched, shrouded fuel rod which was subjected to a power hurst that deposited a total radially averaged energy of 527 cal/g. The primary objectives of the Scoping Test were defined as follows: (1) Determine the applicability of extrapolating low-power steady state calorimetric measurements and self-powered neutron detector (SPND) output to determine fuel rod energy depositions during a power burst. (2) Determine the enerqy deposition failure threshold for unirradiated fuel rods at BWR hot-startup coolant conditions. (3) Determine the magnitudes of oossible pressure pulses resulting from rod failure. (4) Determine the sensitivity of the test instrumentation to high transient radiation exposures. In general, the energy deposition values for the Scoping Test derived from the SPND output were 25% higher than those obtained from the core ion chamber data. Determining which values are correct will require radiochemical analysis of the fuel rods which will take several months. At present, it apoears that the SPND derived energies are in error because of excellent agreement between the calculated and measured power calibration results and the agreement between the predicted failure threshold and that seen using the core ion chamber derived energies. Meeting the second objective was accomplished during the first three test phases by subjecting the fuel rods to energy depositions which bracketed the failure threshold. The failure threshold in terms of total pellet surface energy at the axial flux peak was found to be between 218 cal/g where no rod failure occurred and 256 cal/g where · rod failure did occur. The experiment predictions indicated that the failure threshold would be 262 cal/g at the pellet surface. Only the fourth experiment phase (527 cal/g) resulted in a pressure pulse upon rod failure. The best indication of source pressure was the reading from a 69 MPa EG&G pressure transducer at the flow shroud inlet. This pressure transducer indicated a pressure pulse upon rod failure of 28.2 MPa with a rise time of 1.6 ms. The source pressure was attenuated considerably outside the shroud region as indicated by pressure transducers in the upper plenum of the in-pile tube and in the flow bypass region. The maximum pressure indicated outside the flow shroud was 2.1 MPa. In general, instrumentation sensitivity to radiation was minimal. The most significant instrumentation problem during the power bursts was a false flowrate indication by the flow turbines. This problem is being examined. The Kaman and Bell & Howell pressure transducers showed the least sensitivity to radiation of the pressure measurement devices. The EG&G transducers were most sensitive. The locked linear variable differential transformer (LVDT) gave no indication of radiation sensitivity as its response during the burst was a straight line. The strain gages were very sensitive to radiation, indicating a strain increase of 70% with the second burst of RIA-ST-1. The Type S thermocouple did not exhibit significant radiation sensitivity. In addition, the RIA Scoping Test has provided data on the consequences of fuel rod failure during a RIA event at BWR hot startup conditions. Posttest examination of the fuel rods from the first two phases of the test revealed large quantities of UO{sub 2} fuel missing from the cladding. Fuel rod failures for energy depositions near the failure threshold in previous closed capsule tests without forced coolant flow resulted in only a slight amount of fuel loss

Heart rate variability and the relationship between trauma exposure age, and psychopathology in a post-conflict setting

BACKGROUND: Cumulative exposure to potentially traumatic events (PTEs) increases risk for mental distress in conflict-affected settings, but the psychophysiological mechanisms that mediate this dose-response relationship are unknown. We investigated diminished heart rate variability (HRV) - an index of vagus nerve function and a robust predictor of emotion regulation capacity - as a vulnerability marker that potentially mediates the association between PTE exposure, age and symptoms of posttraumatic stress disorder (PTSD), psychological distress and aggressive behavior, in a community sample from Timor-Leste - a post-conflict country with a history of mass violence. METHOD: Resting state heart rate data was recorded from 45 cases of PTSD, depression and intermittent explosive disorder (IED); and 29 non-case controls. RESULTS: Resting HRV was significantly reduced in the combined case group compared with non-cases (p = .021; Cohen's d = 0.5). A significant mediation effect was also observed, whereby a sequence of increased age, reduced HRV and elevated PTSD symptoms mediated the association between PTE exposure and distress (B = .06, SE = .05, 95% CI = [.00-.217]) and aggression (B = .02, SE = .02, 95% CI = [.0003-.069])). CONCLUSION: The findings demonstrate an association between diminished resting HRV and psychopathology. Moreover, age-related HRV reductions emerged as a potential psychophysiological mechanism that underlies enhanced vulnerability to distress and aggression following cumulative PTE exposure