Evaluating femtosecond laser ablation of graphene on SiO<inf>2</inf>/Si substrate

We demonstrate a uniform single layer micropattern of graphene on 300 nm thick SiO2 on a Si substrate using a 1030 nm, 280 fs laser. The cutting process was conducted in air, the pattern defined through the motion of a high-precision translation stage. Approximately 1.6 μm wide graphene microchannels were cut with uniform widths and well defined edges. The ablation threshold of graphene was determined to be 66–120 mJ/cm2, at which the selective removal of graphene was achieved without damage to the SiO2/Si substrate. Scanning electron microscopy images revealed high quality cuts (standard deviation 40 nm) with little damage or re-deposition. Raman maps showed no discernible laser induced damage in the graphene within the ablation zone. Atomic force microscopy revealed an edge step height ranging from less than 2 to 10 nm, suggesting little removal of SiO2 and no damage to the silicon (the central path showed sub ablation threshold swelling). The effect of the ultrafast laser on the surface potential at the cut edge has been measured and it showed a distinguishable boundary.This work was supported by The Engineering and Physical Sciences Research Council (EPSRC) and National University of Defence Technology (NUDT). The authors also thank Cambridge Graphene Centre (CGC).This is the final version of the article. It first appeared from the American Institute of Physics via http://dx.doi.org/10.2351/1.494451

Characteristics of Duplicate Records in OCLC's Online Union Catalog

Duplicate records in the Online Union Catalog of the OCLC Online Computer Library Center, Inc., were analyzed. Bibliographic elements comprise information found in one or more fields of a bibliographic record; e.g., the author element comprises the main and added author entry fields. Bibliographic element mismatches in duplicate record pairs were considered relative to the number of records in which each element was present. When a single element differed in a duplicate record pair, that element was most often publication date. This finding shows that a difference in the date of publication is not a reliable indicator of bibliographic uniqueness. General cataloging and data entry patterns such as variations in title transcription and form of name, typographical errors, mistagged fields, misplaced subfield codes, omissions, and inconsistencies between fixed and variable fields often caused records that were duplicates to appear different. These factors can make it extremely difficult for catalogers to retrieve existing bibliographic records and thus avoid creating duplicate records. They also prevent duplicate detection algorithms used for tape-loading records from achieving desired results. An awareness of particularly problematic bibliographic elements and general factors contributing to the creation of duplicate records should help catalogers identify and accept existing records more often. This awareness should also help to direct system designers in their development of more sensitive algorithms to be used for tape loading. The resulting general reduction in the number of duplicate records in union catalogs will be a major step toward increased cataloger productivity, user satisfaction, and overall online database quality

Radiative corrections for (e,e′p) reactions at GeV energies

A general framework for applying radiative corrections to (e,e′p) coincidence reactions at GeV energies is presented, with special emphasis to higher-order bremsstrahlung effects, radiation from the scattered hadron, and the validity of peaking approximations. The sensitivity to the assumptions made in practically applying radiative corrections to (e,e′p) data is extensively discussed. The general framework is tested against experimental data of the 1H(e,e′p) reaction at momentum transfer values larger than 1.0 (GeV/c)^2, where radiative processes become a dominant source of uncertainty. The formulas presented here can easily be modified for any other electron-induced coincidence reaction

Three-Dimensional Simulations of Bi-Directed Magnetohydrodynamic Jets Interacting with Cluster Environments

We report on a series of three-dimensional magnetohydrodynamic simulations of active galactic nucleus (AGN) jet propagation in realistic models of magnetized galaxy clusters. We are primarily interested in the details of energy transfer between jets and the intracluster medium (ICM) to help clarify what role such flows could have in the reheating of cluster cores. Our simulated jets feature a range of intermittency behaviors, including intermittent jets that periodically switch on and off and one model jet that shuts down completely, naturally creating a relic plume. The ICM into which these jets propagate incorporates tangled magnetic field geometries and density substructure designed to mimic some likely features of real galaxy clusters. We find that our jets are characteristically at least 60% efficient at transferring thermal energy to the ICM. Irreversible heat energy is not uniformly distributed, however, instead residing preferentially in regions very near the jet/cocoon boundaries. While intermittency affects the details of how, when, and where this energy is deposited, all of our models generically fail to heat the cluster cores uniformly. Both the detailed density structure and nominally weak magnetic fields in the ICM play interesting roles in perturbing the flows, particularly when the jets are non-steady. Still, this perturbation is never sufficient to isotropize the jet energy deposition, suggesting that some other ingredient is required for AGN jets to successfully reheat cluster cores.Comment: 19 pages, 18 figures, Accepted for publication in the Astrophysical Journa

Momentum Transfer Dependence of Nuclear Transparency from the Quasielastic ^(12)C(e, e'p) Reaction

The cross section for quasielastic ^(12)C(e,e’p) scattering has been measured at momentum transfer Q^2=1, 3, 5, and 6.8 (GeV/c)^2. The results are consistent with scattering from a single nucleon as the dominant process. The nuclear transparency is obtained and compared with theoretical calculations that incorporate color transparency effects. No significant rise of the transparency with Q^2 is observed

Elevated glutamatergic compounds in pregenual anterior cingulate in pediatric autism spectrum disorder demonstrated by 1H MRS and 1H MRSI.

Recent research in autism spectrum disorder (ASD) has aroused interest in anterior cingulate cortex and in the neurometabolite glutamate. We report two studies of pregenual anterior cingulate cortex (pACC) in pediatric ASD. First, we acquired in vivo single-voxel proton magnetic resonance spectroscopy ((1)H MRS) in 8 children with ASD and 10 typically developing controls who were well matched for age, but with fewer males and higher IQ. In the ASD group in midline pACC, we found mean 17.7% elevation of glutamate + glutamine (Glx) (p&lt;0.05) and 21.2% (p&lt;0.001) decrement in creatine + phosphocreatine (Cr). We then performed a larger (26 subjects with ASD, 16 controls) follow-up study in samples now matched for age, gender, and IQ using proton magnetic resonance spectroscopic imaging ((1)H MRSI). Higher spatial resolution enabled bilateral pACC acquisition. Significant effects were restricted to right pACC where Glx (9.5%, p&lt;0.05), Cr (6.7%, p&lt;0.05), and N-acetyl-aspartate + N-acetyl-aspartyl-glutamate (10.2%, p&lt;0.01) in the ASD sample were elevated above control. These two independent studies suggest hyperglutamatergia and other neurometabolic abnormalities in pACC in ASD, with possible right-lateralization. The hyperglutamatergic state may reflect an imbalance of excitation over inhibition in the brain as proposed in recent neurodevelopmental models of ASD

Evidence for virtual Compton scattering from the proton

In virtual Compton scattering an electron is scattered off a nucleon such that the nucleon emits a photon. We show that these events can be selected experimentally, and present the first evidence for virtual Compton scattering from the proton in data obtained at the Stanford Linear Accelerator Center. The angular and energy dependence of the data is well described by a calculation that includes the coherent sum of electron and proton radiation

Border Terriers under primary veterinary care in England: demography and disorders

The Border Terrier is a working terrier type that is generally considered to be a relatively healthy and hardy breed. This study aimed to characterise the demography and common disorders of Border Terriers receiving veterinary care in England using de-identified electronic patient record data within the VetCompass™ Programme