Singular field response and singular screening of vacancies in antiferromagnets

For isolated vacancies in ordered local-moment antiferromagnets we show that the magnetic-field linear-response limit is generically singular: The magnetic moment associated with a vacancy in zero field is different from that in a finite field h in the limit h->0. The origin is a universal and singular screening cloud, which moreover leads to perfect screening as h->0 for magnets which display spin-flop bulk states in the weak-field limit.Comment: 5 pages, 4 figs, (v2) 2-page supplement added, final version as publishe

Comparison of linear and non-linear 2D+T registration methods for DE-MRI cardiac perfusion studies

A series of motion compensation algorithms is run on the challenge data including methods that optimize only a linear transformation, or a non-linear transformation, or both – first a linear and then a non-linear transformation. Methods that optimize a linear transformation run an initial segmentation of the area of interest around the left myocardium by means of an independent component analysis (ICA) (ICA-*). Methods that optimize non-linear transformations may run directly on the full images, or after linear registration. Non-linear motion compensation approaches applied include one method that only registers pairs of images in temporal succession (SERIAL), one method that registers all image to one common reference (AllToOne), one method that was designed to exploit quasi-periodicity in free breathing acquired image data and was adapted to also be usable to image data acquired with initial breath-hold (QUASI-P), a method that uses ICA to identify the motion and eliminate it (ICA-SP), and a method that relies on the estimation of a pseudo ground truth (PG) to guide the motion compensation

Development of a 1 GS/s high-resolution transient recorder

With present-day detectors in high energy physics one is often faced with short analog pulses of a few nanoseconds length which may cover large dynamic ranges. In many experiments both amplitude and timing information have to be measured with high accuracy. Additionally, the data rate per readout channel can reach several MHz, which makes high demands on the separation of pile-up pulses. For such applications we have built the GANDALF transient recorder with a resolution of 12bit@1GS/s and an analog bandwidth of 500 MHz. Signals are digitized and processed by fast algorithms to extract pulse arrival times and amplitudes in real-time and to generate experiment trigger signals. With up to 16 analog channels, deep memories and a high data rate interface, this 6U-VME64x/VXS module is not only a dead-time free digitization unit but also has huge numerical capabilities provided by the implementation of a Virtex5-SXT FPGA. Fast algorithms implemented in the FPGA may be used to disentangle possible pile-up pulses and determine timing information from sampled pulse shapes with a time resolution in the picosecond range. Recently the application spectrum has been extended by implementing a 128-channel time-to-digital converter inside the FPGA and an appropriate input mezzanine card

Medical Imaging Decision And Support (MIDAS):Study protocol for a multi-centre cluster randomized trial evaluating the ESR iGuide

Objectives: Medical imaging plays an essential role in healthcare. As a diagnostic test, imaging is prone to substantial overuse and potential overdiagnosis, with dire consequences to patient outcomes and health care costs. Clinical decision support systems (CDSSs) were developed to guide referring physicians in making appropriate imaging decisions. This study will evaluate the effect of implementing a CDSS (ESR iGuide) with versus without active decision support in a physician order entry on the appropriate use of imaging tests and ordering behaviour. Methods: A protocol for a multi-center cluster-randomized trial with departments acting as clusters, combined with a before-after-revert design. Four university hospitals with eight participating departments each for a total of thirty-two clusters will be included in the study. All departments start in control condition with structured data entry of the clinical indication and tracking of the imaging exams requested. Initially, the CDSS is implemented and all physicians remain blinded to appropriateness scores based on the ESR imaging referral guidelines. After randomization, half of the clusters switch to the active intervention of decision support. Physicians in the active condition are made aware of the categorization of their requests as appropriate, under certain conditions appropriate, or inappropriate, and appropriate exams are suggested. Physicians may change their requests in response to feedback. In the revert condition, active decision support is removed to study the educational effect. Results/conclusions: The main outcome is the proportion of inappropriate diagnostic imaging exams requested per cluster. Secondary outcomes are the absolute number of imaging exams, radiation from diagnostic imaging, and medical costs. Trial registration number: Approval from the Medical Ethics Review Committee was obtained under protocol numbers 20–069 (Augsburg), B 238/21 (Kiel), 20–318 (Lübeck) and 2020–15,125 (Mainz). The trial is registered in the ClinicalTrials.gov</p

Volatile organic compounds composition of merged and aged forest fire plumes from Alaska and western Canada

The NOAA WP-3 aircraft intercepted aged forest fire plumes from Alaska and western Canada during several flights of the NEAQS-ITCT 2k4 mission in 2004. Measurements of acetonitrile (CH3CN) indicated that the air masses had been influenced by biomass burning. The locations of the plume intercepts were well described using emissions estimates and calculations with the transport model FLEXPART. The best description of the data was generally obtained when FLEXPART injected the forest fire emissions to high altitudes in the model. The observed plumes were generally drier than the surrounding air masses at the same altitude, suggesting that the fire plumes had been processed by clouds and that moisture had been removed by precipitation. Different degrees of photochemical processing of the plumes were determined from the measurements of aromatic VOCs. The removal of aromatic VOCs was slow considering the transport times estimated from the FLEXPART model. This suggests that the average OH levels were low during the transport, which may be explained by the low humidity and high concentrations of carbon monoxide and other pollutants. In contrast with previous work, no strong secondary production of acetone, methanol and acetic acid is inferred from the measurements. A clear case of removal of submicron particle volume and acetic acid due to precipitation scavenging was observed. Copyright 2006 by the American Geophysical Union

Airborne measurements of carbonaceous aerosol soluble in water over northeastern United States: Method development and an investigation into water-soluble organic carbon sources

[1] A particle-into-liquid sampler (PILS) was coupled to a total organic carbon (TOC) analyzer for 3 s integrated measurements of water-soluble organic carbon (WSOC) in PM 1 ambient particles. The components of the instrument are described in detail. The PILS-TOC was deployed on the NOAA WP-3D aircraft during the NEAQS/ITCT 2004 program to investigate WSOC sources over the northeastern United States and Canada. Two main sources were identified: biomass burning emissions from fires in Alaska and northwestern Canada and emissions emanating from urban centers. Biomass burning WSOC was correlated with carbon monoxide (CO) and acetonitrile (r 2 &gt; 0.88). These plumes were intercepted in layers at altitudes between 3 and 4 km and contained the highest fine particle volume and WSOC concentrations of the mission. Apart from the biomass burning influence, the lowest WSOC concentrations were recorded in rural air masses that included regions of significant biogenic emissions. Highest concentrations were at low altitudes in distinct plumes from urban centers. WSOC and CO were highly correlated (r 2 &gt; 0.78) in these urban plumes. The ratio of the enhancement in WSOC relative to CO enhancement was found to be low ($3 mg C/m 3 /ppmv) in plumes that had been in transit for a short time, and increased with plume age, but appeared to level off at$32 ± 4 mg C/m 3 /ppmv after $1 day of transport from the sources. The results suggest that the production of WSOC in fine particles depends on compounds coemitted with CO and that this process is rapid with a time constant of$1 day. Citation: Sullivan, A. P., R. E. Peltier, C. A. Brock, J. A. de Gouw, J. S. Holloway, C. Warneke, A. G. Wollny, and R. J. Weber (2006), Airborne measurements of carbonaceous aerosol soluble in water over northeastern United States: Method development and an investigation into water-soluble organic carbon sources

The Fast Read-out System for the MAPMTs of COMPASS RICH-1

A fast readout system for the upgrade of the COMPASS RICH detector has been developed and successfully used for data taking in 2006 and 2007. The new readout system for the multi-anode PMTs in the central part of the photon detector of the RICH is based on the high-sensitivity MAD4 preamplifier-discriminator and the dead-time free F1-TDC chip characterized by high-resolution. The readout electronics has been designed taking into account the high photon flux in the central part of the detector and the requirement to run at high trigger rates of up to 100 kHz with negligible dead-time. The system is designed as a very compact setup and is mounted directly behind the multi-anode photomultipliers. The data are digitized on the frontend boards and transferred via optical links to the readout system. The read-out electronics system is described in detail together with its measured performances.Comment: Proceeding of RICH2007 Conference, Trieste, Oct. 2007. v2: minor change