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H Halling

Publications and source records attributed to H Halling.

6 recordsLinked to original sources
PubMed2000

Measurement of rubidium and xenon absolute polarization at high temperatures as a means of improved production of hyperpolarized (129)Xe.

We report on a rubidium-xenon (Rb-Xe) polarization unit for the continuous production of large quantities of hyperpolarized (129)Xe. The unit includes two diagnostic systems which enable the absolute measurement of both the (85)Rb and (129)Xe polarization in situ and at high temperatures. The Rb diagnostic system allows the measurement of one- or two-dimensional images of the absolute Rb polarization and thus enables the experimental study of light penetration into the optical pumping cell. The equilibrium Xe polarization measured in the optical pumping cell and in the freezing unit is typically approximately 20%, under optimal flowing conditions, and this is much lower than the volume-averaged rubidium polarization.

Isotope Labeling↗
PubMed1997

The design of an animal PET: flexible geometry for achieving optimal spatial resolution or high sensitivity.

We present the design of a positron emission tomograph (PET) with flexible geometry dedicated to in vivo studies of small animals (TierPET). The scanner uses two pairs of detectors. Each detector consists of 400 small individual yttrium aluminum perovskite (YAP) scintillator crystals of dimensions 2 x 2 x 15 mm3, optically isolated and glued together, which are coupled to position-sensitive photomultiplier tubes (PSPMT's). The detector modules can be moved in a radial direction so that the detector-to-detector spacing can be varied. Special hardware has been built for coincidence detection, position detection, and real-time data acquisition, which is performed by a PC. The single-event data are transferred to workstations where the radioactivity distribution is reconstructed. The dimensions of the crystals and the detector layout are the result of extensive simulations which are described in this report, taking into account sensitivity, spatial resolution and additional parameters like parallax error or scatter effects. For the three-dimensional (3-D) reconstruction a genuine 3-D expectation-maximization (EM)-algorithm which can include the characteristics of the detector system has been implemented. The reconstruction software is flexible and matches the different detector configurations. The main advantage of the proposed animal PET scanner is its high flexibility, allowing the realization of various detector-system configurations. By changing the detector-to-detector spacing, the system is capable of either providing good spatial resolution or high sensitivity for dynamic studies of pharmacokinetics.

Algorithms↗
PubMed1979

Suspected link between exposure to hexachlorophene and malformed infants.

Retrospective studies, performed in 6 hospitals in Sweden, demonstrated that severe congenital malformations occurred more frequently in neonates born to mothers who used hexachlorophene soaps, 10--60 times a day by handwashing and hand-creams during at least the first trimester of pregnancy (25 severe malformations in 460 neonates), when compared to neonates born to similarly employed mothers who did not use hexachlorophene soaps (0 severe malformations in 233 neonates). Minor congenital anomalies were also more commonly noted in the hexachlorophene-exposed group when contrasted with controls. Other known adverse influences, such as age, infections during pregnancy, other drug usage, or smoking habits did not appear different in the two groups.

Abnormalities, Drug-Induced↗
PubMedDate not supplied

Effect of ascorbic acid on N-nitrosoproline excretion in the urine of lacto-vegetarians and subjects on a free-choice diet.

The amounts of N-nitrosoproline (NPRO) excreted in the urine of lacto-vegetarians and subjects eating a free-choice diet were determined. The study was carried out during four consecutive weeks and specified extra amounts of ascorbic acid were ingested daily during three of them. The average amount of NPRO excreted in the urine of the lacto-vegetarians (1.33 micrograms/24 h) was slightly smaller than that in the urine of the individuals eating a free-choice diet (2.13 micrograms/24 h). Intake of as little as 3 x 20 mg of extra ascorbic acid per day reduced the NPRO excretion. Intake of 3 x 1000 mg of ascorbic acid resulted in a statistically significant decrease in NPRO excretion in the urine.

Adult↗