Physical model of neutron scattering by clathrate hydrate and C60hosting paramagnetic oxygen molecules.

This paper describes the physical modelling of neutron scattering in two polycrystalline inclusion compounds, fully deuterated clathrate hydrate andC60, each with paramagnetic oxygen as guest molecules. For studying the suitability of these materials for neutron moderation to very low energies, the model includes, in addition to the magnetic neutron scattering by the oxygen, the nuclear scattering by all constituents. The theoretical total cross sections are calculated based on the phonon density of states obtained by density functional theory and molecular dynamics simulations. At low temperatures, the developed scattering kernels are in good agreement with experimental neutron scattering data reported in the literature. At 20 K and above, a Lorentzian distribution for the zero-field splitting of the magnetic substates of the spin triplet of the oxygen molecules helps to reproduce magnetic peaks observed in inelastic neutron scattering experiments better than the original theory based on a single-valued splitting constant. Neutron spectra obtained by Monte Carlo simulations in infinite media are presented, highlighting the potential use ofO2-containing fully deuterated clathrate hydrate as a neutron moderator for the production of very cold neutrons.

Superfluid-helium converter for accumulation and extraction of ultracold neutrons.

We report the first successful extraction of accumulated ultracold neutrons (UCN) from a converter of superfluid helium, in which they were produced by downscattering neutrons of a cold beam from the Munich research reactor. Windowless UCN extraction is performed in vertical direction through a mechanical cold valve. This prototype of a versatile UCN source is comprised of a novel cryostat designed to keep the source portable and to allow for rapid cooldown. We measured time constants for UCN storage and extraction into a detector at room temperature, with the converter held at various temperatures between 0.7 and 1.3 K. The UCN production rate inferred from the count rate of extracted UCN is close to the theoretical expectation.

First Ever Storage of Ultracold Neutrons in a Magnetic Trap Made of Permanent Magnets.

Further improvement in the accuracy of any neutron lifetime experiment by means of ultracold neutrons (UCN) in material bottles is limited due to unavoidable systematic effects when the UCN are reflected from the walls. However, such effects can be excluded in principle if magnetic trapping of UCN is used. The storage of UCN in a small magnetic trap made of permanent magnets was demonstrated for the first time ever. The measured storage time in this feasibility study was (882 ± 16) s. At this level of accuracy no depolarization was observed.

A Superconducting Magnet UCN Trap for Precise Neutron Lifetime Measurements.

Finite-element methods along with Monte Carlo simulations were used to design a magnetic storage device for ultracold neutrons (UCN) to measure their lifetime. A setup was determined which should make it possible to confine UCN with negligible losses and detect the protons emerging from ß-decay with high efficiency: stacked superconducting solenoids create the magnetic storage field, an electrostatic extraction field inside the storage volume assures high proton collection efficiency. Alongside with the optimization of the magnetic and electrostatic design, the properties of the trap were investigated through extensive Monte Carlo simulation.

Is the unitarity of the quark-mixing CKM matrix violated in neutron beta-decay?

We report on a new measurement of neutron beta-decay asymmetry. From the result A(0) = -0.1189(7), we derive the ratio of the axial vector to the vector coupling constant lambda = g(A)/g(V) = -1.2739(19). When included in the world average for the neutron lifetime tau = 885.7(7) s, this gives the first element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix V(ud). With this value and the Particle Data Group values for V(us) and V(ub), we find a deviation from the unitarity condition for the first row of the CKM matrix of Delta = 0.0083(28), which is 3.0 times the stated error.

[Acute pyelonephritis in children with minimal or normal urine findings]. / Akutt pyelonefritt ved sparsomme eller normale urinfunn hos barn.

BACKGROUND: Over the past years we have seen several children with serious bacterial infections in whom the focus of the infection was found in the kidneys despite of normal or minimal urine findings. MATERIAL AND METHODS: We review the cases of all children hospitalised at our paediatric department from 1995-2000 with normal or minimal urine findings, and in whom acute pyelonephritis was diagnosed by means of computerized tomographic imaging of the kidneys. RESULTS: All 10 children (aged 9 months to 9 years) had focal areas of decreased enhancement in the kidney parenchyma. All received intravenous antibiotic treatment. Vesicouretheral reflux was detected in four patients and required surgical intervention in one. One patient had considerable renal scarring and decreased renal function on dimercaptosuccinic acid (DMSA) scintigraphy. INTERPRETATION: In children with suspected serious bacterial infection, it is important to have the possibility of renal infection in mind in spite of normal urine findings. The importance of establishing the right diagnosis lies in the fact that patients with pyelonephritis need further investigation and follow-up.

Effect of the lipoxygenase inhibitor N-hydroxy-N-(6-methoxy-3,4-dihydro-2-naphthylmethyl)urea on bronchoconstriction and lung vascular permeability in anaphylactic guinea pigs.

Narrowing of the airway lumen as a result of plasma exudation could augment airflow obstruction after allergen-induced bronchoconstriction. Because leukotrienes are putative mediators of bronchial asthma, the effects of a lipoxygenase inhibitor, VZ564 (N-hydroxy-N-(6-methoxy-3,4-dihydro-2- naphthylmethyl) urea. CAS 147495-99-6), on increased pulmonary permeability and bronchoconstriction during anaphylactic reaction were studied in guinea pigs and compared to the effects of the phosphodiesterase inhibitor theophylline. An anaphylactic reaction was induced by ovalbumin challenge (0.2 mg/kg i.v.) in passively sensitized and antihistamine (mepyramine)-pretreated guinea pigs; bronchoconstriction was measured as increased intratracheal pressure; lung vascular permeability was evaluated as extravasation of Evans blue dye up to 10 min after antigenic challenge. Ovalbumin challenge induced an increase in intratracheal pressure by 31 +/- 3 mmHg; the pulmonary permeability index was higher in ovalbumin-challenged versus saline (sham)-challenged guinea pigs (1.49 +/- 0.17 vs 0.56 +/- 0.04, p < 0.05). VZ564 and theophylline dose-dependently reduced increased pulmonary permeability and bronchoconstriction. VZ564 (10 and 46.4 mg/kg p.o., given 1 h before ovalbumin challenge) inhibited increased lung permeability by 42% and 95% and reduced bronchoconstriction by 61% at the higher dose. Theophylline (1 and 10 mg/kg i.v., given 10 min before ovalbumin challenge) diminished increased pulmonary permeability by 88% and reduced bronchoconstriction by 63% at the higher dose. In conclusion, the novel lipoxygenase inhibitor VZ564 inhibits after oral application important symptoms of asthma, namely bronchoconstriction and alveolar exudation of plasma in anaphylactic guinea pigs. The acute effects of VZ564 in this experimental model are comparable with the effects of the well known antiasthmatic substance theophylline.

(dA-dT) dependent inactivation of the DNA template properties by interaction with netropsin and distamycin A.

The inhibitory effect of the polypeptide antibiotics netropsin and distamycin A on DNA dependent nucleic acid synthesis has been shown to be related to the base composition of the template DNA. A number of natural DNA's of quite different dA-dT content as well as poly (dI-dC)-poly (dI-dC), poly (dA-dT)-poly (dA-dT), poly (dA) - poly (dT) and poly (dG) - poly (dC) has been studied as templates in DNA and in part in RNA polymerase reaction. The highest binding efficiency of netropsin existing for (dA-dT) - containing DNA polymers and the less pronounced interaction with the (dI-dC)-containing polymer shown by the melting and CD spectrral behaviour of the complexes are entirely reflected in the template inactivation. The same is evident for distamycin A. However, in contrast to netropsin the antibiotic distamycin A exhibits some binding tendency to poly (dG) - poly (dC). Binding effects of a netropsin derivative to DNA and (dA-dT) -containing polymers suggest the importance of hydrogen bonds of the peptide groups in the complex formation.