Long-term Atmospheric Mercury Wet Deposition at Underhill, Vermont

Section 112(m) of the 1990 Clean Air Act Amendments, referred to as the Great Waters Program, mandated an assessment of atmospheric deposition of hazardous air pollutants (HAPs) to Lake Champlain. Mercury (Hg) was listed as a priority HAP and has continued to be a high priority for a number of national and international programs. An assessment of the magnitude and seasonal variation of atmospheric Hg levels and deposition in the Lake Champlain basin was initiated in December 1992 which included event precipitation collection, as well as collection of vapor and particle phase Hg in ambient air. Sampling was performed at the Proctor Maple Research Center in Underhill Center, VT. The range in the annual volume-weighted mean concentration for Hg in precipitation was 7.8–10.5 ng/l for the 11-year sampling period and the average amount of Hg deposited with each precipitation event was 0.10 μg/m 2 . The average amount of Hg deposited through precipitation each year from 1993 to 2003 was 9.7 μg/m 2 /yr. A seasonal pattern for Hg in precipitation is clearly evident, with increased Hg concentrations and deposition observed during spring and summer months. While a clear trend in the 11-year event deposition record at Underhill was not observed, a significant decrease in the event max-to-monthly ratio was observed suggesting that a major source influence was controlled over time. Discrete precipitation events were responsible for significant fractions of the monthly and annual loading of Hg to the forested ecosystem in Vermont. Monthly-averaged temperatures were found to be moderately correlated with monthly volume-weighted mean Hg concentrations ( r 2 =0.61) and Hg deposition ( r 2 =0.67) recorded at the Vermont site. Meteorological analysis indicated the highest levels of Hg in precipitation were associated with regional transport from the west, southwest, and south during the warmer months.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44444/1/10646_2004_Article_6260.pd

Laser Induced Visual Pigment Conversions in Fly Photoreceptors Measured in vivo

The photochemical cycle of fly visual pigment was studied in vivo with laser methods. Two pulsed dye lasers were used, one delivering the visual pigment converting flash and the other testing the pigment state after a variable interval. Transmission through the rhabdomeres was measured in the eye of blowfly Calliphora erythrocephala. It followed that rhodopsin R490 converts into metarhodopsin M580 via two intermediates, with time constants of 700 ns and 80 µs respectively. In the reverse pathway, i.e. the photoconversion of metarhodopsin into rhodopsin, an intermediate decaying with a time constant of 4 µs was found

Unified multiple‐feature color display for MR images

A display method is proposed in which the spin‐lattice relaxation time T 1, the spinspin relaxation time T 2, and the proton density ρ of each pixel in a MR image are simultaneously expressed in color features in a unified way that allows international standardization. MR images were made from a phantom, a healthy volunteer, and patients in such a way that T 1 and T 2 and proton density images could be derived. T 1 and T 2 data were compared with accurate relaxation time measurements of the phantom content. Color images were computed from the acquired T 1 and T 2 images using matrix multiplication on a pixel base. In this way the color combination in each pixel represents the properties of that particular pixel by a unique mixing of the elementary colors red, green, and blue. Color resolution could be modified using different choices of the reference triangle in which the color combinations were defined. This method of representation offers a means for displaying multiple features as T 1, and T 2 in one directly interpretable image, independent of instrumental settings. © 1989 Academic Press, In

Pervasive access to images and data--the use of computing grids and mobile/wireless devices across healthcare enterprises.

Contains fulltext : 51535.pdf (publisher's version ) (Closed access)Emerging technologies are transforming the workflows in healthcare enterprises. Computing grids and handheld mobile/wireless devices are providing clinicians with enterprise-wide access to all patient data and analysis tools on a pervasive basis. In this paper, emerging technologies are presented that provide computing grids and streaming-based access to image and data management functions, and system architectures that enable pervasive computing on a cost-effective basis. Finally, the implications of such technologies are investigated regarding the positive impacts on clinical workflows

Het EPD is geen wondermiddel.

Contains fulltext : 51629.pdf (publisher's version ) (Closed access

Het EPD als panacee voor problemen in de zorg?

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Arm raising at exposure-controlled multidetector trauma CT of thoracoabdominal region: higher image quality, lower radiation dose.

Contains fulltext : 69921.pdf (publisher's version ) (Closed access)PURPOSE: To evaluate the effect of arm position on image quality and effective radiation dose in an automatic exposure-controlled (AEC) multidetector thoracoabdominal computed tomography (CT) protocol in trauma patients. MATERIALS AND METHODS: This retrospective study of the data of 177 trauma patients (117 male; median age, 39 years) was approved by the institutional ethics board, with informed patient consent waived. Patients underwent scanning by using an AEC 16-detector thoracoabdominal CT protocol in which both arms were raised above the shoulder region (standard-position group, 132 patients), one arm was raised and the other was down (one-arm group, 27 patients), or both arms were down (two-arm group, 18 patients). Objective and subjective image quality was assessed. Individual effective radiation dose was calculated from the effective tube current-time product per exposed section. For this purpose, section location-dependent conversion factors were derived by using a CT dosimetry calculator. The effect of arm position on effective dose was quantified by using linear regression analysis with correction for patient volume and attenuation. RESULTS: Compared with the image quality in the standard-position group, the image quality in the one- and two-arm groups was decreased but within acceptable diagnostic limits. The median corrected effective dose in the standard-position group was 18.6 mSv; the dose in the one-arm group was 18% (95% confidence interval: 11%, 25%) higher than this, and that in the two-arm group was 45% (95% confidence interval: 34%, 57%) higher. CONCLUSION: Omitting arm raising results in lower but acceptable image quality and a substantially higher effective radiation dose. Hence, effort should be made to position the arms above the shoulder when scanning trauma patients. Clinical trial registration no. NCT00228111