The CTA Sensitivity to Lorentz-Violating Effects on the Gamma-Ray Horizon

The arrival of TeV-energy photons from distant galaxies is expected to be affected by their QED interaction with intergalactic radiation fields through electron-positron pair production. In theories where high-energy photons violate Lorentz symmetry, the kinematics of the process $\gamma + \gamma\rightarrow e^+ + e^-$ is altered and the cross-section suppressed. Consequently, one would expect more of the highest-energy photons to arrive if QED is modified by Lorentz violation than if it is not. We estimate the sensitivity of Cherenkov Telescope Array (CTA) to changes in the $\gamma$-ray horizon of the Universe due to Lorentz violation, and find that it should be competitive with other leading constraints.Comment: 13 pages, 4 figures, typos corrected + references added, results unchanged. Matches version accepted by JCA

STM and Electrochemical Investigation of Homoepitaxial Boron-Doped CVD Diamond Films

Homoepitaxial growth of boron-doped CVD diamond films was carried out on (100) and (111) oriented substrates. Atomic resolution images were obtained for both (100) and (111) surfaces using scanning tunneling microscopy. STM images reveal the presence of a 2x1-monohydride reconstruction for the untreated (100) surface and a lxl reconstruction for the untreated (111) surface. No other atomically resolved reconstructions were observed under a wide range of growth conditions. Non-aqueous electrochemical investigations were carried out on the films exhibiting atomically resolved reconstructions. Evidence for potential-induced surface-reconstruction and surface chemical modification of the (100) 2xl-monohydride surface has been observed

Boron-Doped Homoepitaxial Diamond (100) Film Investigated by Scanning Tunneling Microscopy

Conducting epitaxial diamond films of high quality are essential for many diamond studies and diamond electronic device fabrication. We have grown boron-doped epitaxial diamond films on type Ila natural diamond (100) substrates by microwave plasma chemical vapor deposition. A gas mixture of H2/CH4 was used. Boron doping was done by placing solid sources of pure boron in the microwave plasma. Homoepitaxial films with atomic smoothness were achieved under the following growth conditions: substrate temperature 900 °C, gas pressure 40 Torr, and gas flow rates of H2/CH4 = 900/7.2 seem. The growth rate was 0.87 µm/hr. Surfaces of the homoepitaxial films were studied by scanning tunneling microscopy (STM). STM images show smooth and continuous surface with ripple-like features on micrometer scale. On nanometer scale, alternating terraces of 2x1 and 1x2 dimerization were clearly observed

Microwave Plasma Chemical Vapor Deposited Diamond Tips for Scanning Tunneling Microscopy

Diamond microparticles were grown on etched tungsten wires using a microwave plasma-assisted chemical vapor deposition process. The apexes on cubo-octahedral particles bound by {100} and {111} facets were effectively used as tunneling tips for scanning tunneling microscopy. The atomically resolved surface image of highly oriented pyrolytic graphite was acquired. Tunneling characteristics revealed a higher electron emission from the diamond tips than that from the platinum–iridium tips. The same diamond tips were used to produce surface indentation and its image. © 1997 American Institute of Physics

A Diamond Thin Film Flow Sensor

We present the results of theoretical modeling and experimental testing of a diamond thin film sensor for flow studies. It is shown that the high thermal conductivity of a diamond film can enhance the frequency response of the flow sensor. One-dimensional heat diffusion equation was solved using the finite difference method for determining the frequency response. Two different sensor structures were analyzed: a Ni film on a quartz substrate (Ni/Q) and an intermediate layer of diamond film between the Ni film and quartz substrate (Ni/D/Q). The theoretical model predicts a frequency response for the Ni/D/Q sensor higher than that of the Ni/Q sensor. Diamond films for the Ni/D/Q sensor were deposited onto the quartz substrate by microwave plasma-enhanced chemical vapor deposition (MPECVD). The conditions for a high nucleation density were established for obtaining a continuous diamond thin film. A subsequent nickel film patterned and deposited serves as the sensing arm in the bridge circuit of an anemometer. The measured frequency response of the Ni/D/Q sensor combination is greater than 220 kHz, as compared to the Ni/Quartz sensor response of 120 kHz

Chemical Vapor Deposited Diamond Films for Self-Referencing Fiber Optic Raman Probes [Erratum]

Diamond thin films grown by the microwave plasma enhances chemical vapor deposition (CVD) process have been investigated as an internal reference in fiber optic remote Raman sensing. The growth parameters have been optimized for diamond thin films on quarts substrates using a gas mixture of methane, carbon dioxide, and hydrogen. The resulting films exhibit essentially no Raman spectral background while exhibiting a strong Raman peak at 1332 cm-¹. The films are used as an internal reference in the quantitative measurement of chemical concentration using remote fiber optic Raman sensing. Internal referencing is accomplished by normalizing all spectral intensities of the chemical species to the integrated area of the CVD diamond reference peak at 1332 cm-¹ and verified using ethanol/water solutions. It is shown that the measurement is independent of laser power fluctuations

Area-aggregated assessments of perceived environmental attributes may overcome single-source bias in studies of green environments and health: results from a cross-sectional survey in southern Sweden

Most studies assessing health effects of neighborhood characteristics either use self-reports or objective assessments of the environment, the latter often based on Geographical Information Systems (GIS). While objective measures require detailed landscape data, self-assessments may yield confounded results. In this study we demonstrate how self-assessments of green neighborhood environments aggregated to narrow area units may serve as an appealing compromise between objective measures and individual self-assessments. Methods The study uses cross-sectional data (N = 24,847) from a public health survey conducted in the county of Scania, southern Sweden, in 2008 and validates the Scania Green Score (SGS), a new index comprising five self-reported green neighborhood qualities (Culture, Lush, Serene, Spacious and Wild). The same qualities were also assessed objectively using landscape data and GIS. A multilevel (ecometric) model was used to aggregate individual self-reports to assessments of perceived green environmental attributes for areas of 1,000 square meters. We assessed convergent and concurrent validity for self-assessments of the five items separately and for the sum score, individually and area-aggregated. Results Correlations between the index scores based on self-assessments and the corresponding objective assessments were clearly present, indicating convergent validity, but the agreement was low. The correlation was even more evident for the area-aggregated SGS. All three scores (individual SGS, area-aggregated SGS and GIS index score) were associated with neighborhood satisfaction, indicating concurrent validity. However, while individual SGS was associated with vitality, this association was not present for aggregated SGS and the GIS-index score, suggesting confounding (single-source bias) when individual SGS was used. Conclusions Perceived and objectively assessed qualities of the green neighborhood environment correlate but do not agree. An index score based on self-reports but aggregated to narrow area units can be a valid approach to assess perceived green neighborhood qualities in settings where objective assessments are not possible or feasible.

Chemical Vapor Deposited Diamond Films for Self-Referencing Fiber Optic Raman Probes

Diamond thin films grown by the microwave plasma enhances chemical vapor deposition (CVD) process have been investigated as an internal reference in fiber optic remote Raman sensing. The growth parameters have been optimized for diamond thin films on quarts substrates using a gas mixture of methane, carbon dioxide, and hydrogen. The resulting films exhibit essentially no Raman spectral background while exhibiting a strong Raman peak at 1332 cm-¹. The films are used as an internal reference in the quantitative measurement of chemical concentration using remote fiber optic Raman sensing. Internal referencing is accomplished by normalizing all spectral intensities of the chemical species to the integrated area of the CVD diamond reference peak at 1332 cm-¹ and verified using ethanol/water solutions. It is shown that the measurement is independent of laser power fluctuations

Area-aggregated assessments of perceived environmental attributes may overcome single-source bias in studies of green environments and health: results from a cross-sectional survey in southern Sweden

<p>Abstract</p> <p>Background</p> <p>Most studies assessing health effects of neighborhood characteristics either use self-reports or objective assessments of the environment, the latter often based on Geographical Information Systems (GIS). While objective measures require detailed landscape data, self-assessments may yield confounded results. In this study we demonstrate how self-assessments of green neighborhood environments aggregated to narrow area units may serve as an appealing compromise between objective measures and individual self-assessments.</p> <p>Methods</p> <p>The study uses cross-sectional data (N = 24,847) from a public health survey conducted in the county of Scania, southern Sweden, in 2008 and validates the Scania Green Score (SGS), a new index comprising five self-reported green neighborhood qualities (Culture, Lush, Serene, Spacious and Wild). The same qualities were also assessed objectively using landscape data and GIS. A multilevel (ecometric) model was used to aggregate individual self-reports to assessments of perceived green environmental attributes for areas of 1,000 square meters. We assessed convergent and concurrent validity for self-assessments of the five items separately and for the sum score, individually and area-aggregated.</p> <p>Results</p> <p>Correlations between the index scores based on self-assessments and the corresponding objective assessments were clearly present, indicating convergent validity, but the agreement was low. The correlation was even more evident for the area-aggregated SGS. All three scores (individual SGS, area-aggregated SGS and GIS index score) were associated with neighborhood satisfaction, indicating concurrent validity. However, while individual SGS was associated with vitality, this association was not present for aggregated SGS and the GIS-index score, suggesting confounding (single-source bias) when individual SGS was used.</p> <p>Conclusions</p> <p>Perceived and objectively assessed qualities of the green neighborhood environment correlate but do not agree. An index score based on self-reports but aggregated to narrow area units can be a valid approach to assess perceived green neighborhood qualities in settings where objective assessments are not possible or feasible.</p